BIOS 2

Temperature affects the reaction speed

An enzyme works best at a certain temperature, the optimum temperature. At lower temperatures, the reaction slows down. At a high temperature, the enzyme is denatured. Reactions that take place in the human body normally have an optimum temperature of about 37 ° C, while reactions in plants often have an optimum temperature around 10-20 C.

Lifestyle and cancer

Gene tests can determine if certain mutations are inherited. It is particularly relevant to carry out such tests on persons belonging to families with a frequency of certain cancers that occur early in life. People who do not carry the gene defect will not be at increased risk of developing disease. Although one is inherited for cancer, through a healthy lifestyle it is possible to prevent the disease from developing. A healthy lifestyle reduces the likelihood of spontaneous mutations. Cancer can probably be prevented to a considerable extent by a conscious lifestyle. In particular, some cancers are associated with lifestyle and which can thus be avoided. Among other studies, studies from the United States indicate that 10% of cancer cases are caused by obesity. Mole cancer has a lot to do with tanning. Here, it is UV radiation (ultraviolet radiation) that acts as carcinogen. In particular, sunburn in childhood presents a risk of developing a disease. The risk further increases for people with a delicate, light and freckled skin that easily gets sunburnt. By avoiding being in the sun in the middle of the day in the summer, but rather covering yourself with clothes, you can easily prevent mole cancer. Sunscreen with high sun factor does not effectively protect against all UV rays. In addition, modest amounts of sun on the skin will make the body produce enough vitamin D. It can counteract cancer. Risk of nephropathy increases with a high fat diet The reason may be that fatty foods cause a large amount of bile acid to be excreted in the intestine. Bile acid can further be converted into carcinogenic substances which increase the frequency of mutation one in the gut. Fruits and vegetables with their high content of vitamins, minerals and fiber seem to prevent colon cancer. About 5 of all colon cancer cases are hereditary. For some forms of Tamil cancer, the mutated gene is known, and the likelihood of developing hereditary thick. As much as S0% of all cases of lung cancer have tobacco smoking as a direct cause. This is because tobacco smoke contains carcinogens that increase the frequency of mutations in cells in the lungs. But only 10% of big smokers develop lung cancer. One probable cause for this is that these individuals may be particularly susceptible to lung cancer because they have a low level of DNA repair enzymes (see page 138) and are therefore unable to repair damage to the genetic material effectively. Low-level smokers of a particular repair enzyme have 5-10 times higher risk of developing cancer than high-level smokers of the same enzyme, and 120 times greater cancer is between 80 and 100% for some such forms. risk than non-smokers. Breast cancer is the leading cause of cancer death worldwide among women All women are at risk of developing the disease, and it is less likely to have a connection with lifestyle than other cancers. A hereditary factor is involved in 5-10% of cases. The disease appears to be related to the level of estrogen in the body and therefore increases somewhat with the use of birth control pills using estrogen medication at menopause. Many child births, childbirth at a young age and breastfeeding of children can reduce the risk. Other factors that can further reduce the risk of breast cancer are a healthy lifestyle with olive oil, vitamin A and possibly dietary fiber, physical activity, normal body weight and moderation with alcohol. Early onset of menstruation and high age (over 50 years) are examples of factors that increase the likelihood of getting breast cancer and which have nothing to do with lifestyle. In general, it seems that the diet can help reduce the risk of several cancers. A lot of fruits and especially raw vegetables are good, probably because they contain antioxidants that prevent mutations, moreover, fiber is important. Physical activity also seems to be able to prevent cancer.

Point mutations

Point mutations changes in one base or Point mutations are a few bases. Replacing a base with o others within a gene will cause a codon to change. We call that a substitution. Because most amino acids have more than one codon, such mutations do not have any effect. But in some cases, a change in a codon will result in an altered amino acid in the finished protein. This can then cause the protein to lose its normal function. Sickle cell anemia is an example that a substitution can have serious consequences. Sickle cell anemia is a disease that is found especially among people of African descent. The disease is caused by a single mutation in the gene that encodes hemoglobin, a protein found in the red blood cells, and which carries oxygen. One base is replaced by the gene (A → T), and a single amino acid (glutamic acid) is replaced by another (valine). This altered protein binds oxygen more poorly and produces sickle-shaped red blood cells that can clog the small blood vessels (capillary veins). Oxygen transport is restricted. It leads to fatigue, damage to organs, brain damage, paralysis and high mortality. However, only individuals who have two versions of the mutated gene (homozygous recess) get this disease. However, individuals who have a healthy gene in a mutated gene (heterozygous) are less susceptible to malaria than individuals who have two versions of the healthy allele ( homozygous dominant). This suggests that the malaria parasite (Plasmodnum falciparum) grows more poorly in red blood cells from healthy heterozygous individuals than in homozygous healthy ones. Therefore, in areas with a high degree of malaria, heterozygous carriers will have a higher chance of survival and will therefore pass on the diseased allele. 1 In Central Africa, where malaria occurs, the incidence of the diseased allele is 10%. This is an example of how interaction between heritage and the environment can affect people's health. More serious than single base yields, it would normally be if a gene loses a base or gets one or more bases extra. When a gene loses bases, it is called deletion. When a gene gets extra bases, it is called insertion. We can illustrate this with a simple sentence. On page 193 you read about inheriting hemorrhagic disease. This disease is due to an insertion of a longer base sequence. The result is that a protein (coagulation factor VIII) that is crucial for blood flow is not active. An example of a deleterious disease is cystic fibrosis (CF). This disease is caused by a failure in the transport of water and salts into and out of the cells, especially in the lungs and intestines. Large amounts of viscous mucus are formed, and this greatly reduces the function of the lungs. In some cases, lung transplantation is necessary. Another deleterious disease is Cri du chat, the cat screaming syndrome. The name comes from children with the disease crying and sounds reminiscent of cat maw. This disease also causes moderate to severe developmental disorders. Because mRNA is read as a series of triplets, one extra or one missing base will change the grouping of triplets. We call this a change in reading frame. Near the end of the gene, there are no major consequences, but otherwise, this error will cause so many changes in the finished protein that it cannot function normally. A change in the reading frame often results in the formation of a stop codon that terminates translation and the protein is truncated. Point mutations can occur in connection with DNA copying, DNA repair or cross-over. Such changes occur spontaneously all the time. It is estimated that one of 10 "nucleotides is altered and passed on to the next generation of cells. Point mutations can also be caused by bases being altered by effects from the external environment. Physical or chemical influences that can lead to mutations, we call mutagens. Examples of mutagens are ultraviolet radiation, x-ray radiation, radioactive radiation, heat and also chemicals that react with the bases in the DNA and change them chemically or cause errors in the copying of the DNA. leading to frequent mutations are often carcinogenic, we call them carcinogens, that carcinogens can lead to the development of cancer, because genes that encode regulatory proteins are also mutated, and cell growth gets out of control.

Use of genetically modified plants and animals

The skepticism about genetically modified plants is particularly great in Europe. While Norway has not approved any GMO plants for cultivation in open fields, GMO plants in the United States account for a large part of agricultural production of maize, soy and cotton. Argentina, Brazil, Canada and China also have a significant share of such plants in their agriculture. There have been two main purposes of genetically modifying plants for food production. Firstly, the aim has been to reduce the crop loss by making the plants resistant to herbicides, insects, viruses and fungi - or against frost, ie cultivation properties. Secondly, there has been an aim to improve certain properties of plants used for food, e.g. by increasing the nutritional content, improving the taste, delaying the maturation or increasing the shelf life, dys. food quality. Soybeans have, among other things, been inserted a gene that makes them resistant to the herbicide gyphosate, which is one of the most widely used herbicides on the market. Thus, the farmer can in theory reduce the use of herbicides. In 2010, about 80% of the soy produced in the world was genetically modified. Whole two-thirds of all cooked food contains a soy-based ingredient. Another example is cotton plants with an inserted gene that encodes on insecticide. The plants thus produce the toxin itself and become toxic to pests. Both humans and the environment are thus saved from excessive use of pesticides against insects. Half of the world's population is covered by most of their energy needs by eating rice. Because rice does not contain vitamin A, many people have health problems, especially in Asia. In the body, vitamin A is transformed into visual purity (visual pigments), which we must have in order to see. Vitamin A deficiency causes people to become blind. One type of rice was genetically modified by inserting a beta carotene gene. This type of rice is often called golden rice because of the yellow color from the beta carotene. Beta carotene is converted to vitamin A in the body and then to visual acuity. But this rice variety could not be grown in the fields, and it produced too small amounts of vitamin A to prevent deficiency diseases. A new variant of golden rice has now been developed. It is based on a rice variety that was grown in the fields and may come on the market in a few years. It is shown that the rice works. One cup of golden rice per day is enough to meet the daily need for vitamin A. This rice is expected to be approved for cultivation in a number of Asian countries over the next few years. Genetic modification can provide food with many good properties and lead to greater production. But the cause of hunger today is not lack of food, but lack of fair distribution of food. That is a problem the modification cannot solve. Attempts have been made to insert the growth hormone gene in livestock to make them grow faster. The trials have so far been unsuccessful due to undesirable effects. The animals in some cases had congenital weaknesses, or they suffered strain injuries. It has been more successful to provide cows with genetically engineered growth hormones to increase milk production. In Norway, the use of genes for growth hormones in animal production is prohibited. American scientists have produced a genetically modified salmon with inserted copies of genes for growth hormones. This salmon grows up to six times as fast as normal salmon. Because of general skepticism about genetically modified foods, it may seem that GMO animals will be most important as "pharmaceutical factories", because they can produce large amounts of proteins that can be used as medicines, and such proteins can be extracted from the milk as they genetically modified cows produce. In recent years, researchers have initiated the development of chickens that can be used to produce medical proteins. The interesting proteins accumulate in the egg white in large quantities and can be purified in a cheaper way than the proteins from milk. There are arguments in favor of and against genetic modification. The table gives an overview of some arguments related to the genetic modification of plants and animals in agriculture

Gene regulation in eukaryotic cells

When many copies of a protein are produced in a cell, we say that the gene encoding the protein is highly expressed. Similarly, we say about a gene that gives rise to few or no copies of a protein, that it is poorly expressed or not expressed. The information stored in the DNA is transmitted to active proteins through many steps. Each of these steps is a possible checkpoint that can be regulated so that gene expression is turned on or off or regulated in strength. We will take a closer look at some of these steps. in Epigenetic regulation: When changes in gene expression are due to the genome being changed without altering the nucleotide sequence in the DNA, we call it epigenetic gene regulation. As we have seen, almost all of the body's cells contain the same genetic material. Nevertheless, it is very different which genes are expressed and how much they are expressed in the different ones cell types. Genes that are not needed in one cell type are "turned off", while necessary household genes are always "turned off". During the development of an organism, the fertilized egg cell, the zygote, differentiates into tissue and cell types with specialized tasks, such as nerves, muscles, skin, blood cells, etc. It happens by activating some genes while others become inactive. Such epigenetic mechanisms may also be influenced by a variety of other factors, such as diet, chemicals, and aging. We will return to that in the next chapter. Change in the way the DNA is packed into the nucleus is a form of epigenetic regulation. Previously, you have read about how the DNA is wrapped around histones that are assembled into nucleosomes that form chromatin - packed DNA. Parts of the DNA in the chromosomes can be so tightly packed that genes found here cannot be transcribed into RNA. Such genes are turned off. Roughly speaking, genes in tightly packed DNA regions (chromatin) will be off, while genes in loosely packed areas will be on. This seems to be a way cells can use to prevent the expression of genes from large parts of the genetic material. It becomes a bit like "storing" a lot of information in a book. The text exists, but we can only read it where we open the book. Dense packaging of DNA may be the result of methylation. Methylation means that a methyl group, -CH2, attaches to the DNA. Most often this occurs on the base cytosine in places where this base is "neighbor" with guanine on the same tree. The methylated DNA indicates that proteins will bind to the deleterious site. Because of the proteins, the DNA becomes tightly packed, and then it cannot express genes. Methylation of DNA can also prevent the binding of proteins necessary for transcription of genes. The stories can also be changed, by methylation or by other means. Such alterations of the histones may result in looser or denser packaging such that the genes are expressed respectively. strong or weak. The figure at the bottom right of the previous page shows this. In all cases, the nucleotide sequence in the genetic material is unchanged. Regulation of transcription: For most genes, regulation of the transcription from DNA to RNA is the most important checkpoint. The transcription of the individual genes is controlled by proteins that we call transcription factors. We can also call them control proteins. Different cell types will transcribe different genes, and the different genes will be transcribed differently. Eukaryotic cells have some general control proteins that are required for the transcription of all genes, and some specific control proteins that regulate how many mRNA copies to be produced by each gene. However, as we have seen, transcription is dependent on such control proteins being able to bind to DNA and is not hindered by epigenetic changes in the genome, for example, that the DNA is methylated or too tightly packed. Other important steps where gene regulation can take place: regulation of RNA splicing regulation of mRNA degradation regulation of translation into protein (translation) regulation of protein activity.

Genetic Investigations - Opportunities and Problems Analyzes

to examines which gene variants a person has are called gene embolism or gene tests. Genetic examinations performed on a sick patient to diagnose. is called a diagnostic gene test. However, if the screening is done on a healthy person, the gene test can tell - the gerson is borne of disease genes that will be able to cause disease in the next generation (cicatrized gene diagnostic gene test, eg blood disease) the gerson will certainly develop hereditary disease later in life (so-called stress tomato gene testing, eg Huntington's disease) The persimmon is predisposed to developing hereditary diseases (cyclically preaching gene test Eek's breast cancer) Gene testing can also be performed on newborns, fetuses and embryos. The premise that genetic testing for a disease could be carried out is that the base sequence for fish and suck variants of the disease gene is known. Today, they are utter nests for more than 1,000 diseases of human beings. There is reason to believe that more tests will be developed. In particular, there are certain diseases that are associated with specific allelic variants of one particular. so-called momogenic diseases, it is possible to develop genetic tests for. Some of these diseases are caused by dominant alleles. This means that if you have inherited one allele with a gene defect, the disease will develop. If one of your parents has is Huntington's disease. the disease due to gene defect in one allele, there is a 50% probability that you will get sick. An example of a dominant genetic disease It is a nervous disease that first breaks out in the 30-50s. The disease disables the patient by twitching and unsteady movements and leads to dementia and death after many years of illness. Because there is currently no effective treatment for the disease, one allele with gene defect results in a deadly outcome for all individuals inheriting it. A major problem for possible armies is that at the time they want to start a family, they do not know if they themselves carry the gene defect and can subsequently develop the disease, and if it will then progress quickly. However, a gene test can identify individuals with gene defects if the symptoms show up. Then a person with the gene defect will be able to choose whether or not to have children. As we have mentioned, familial hypercholesterolemia is another dominant genetic disease. Unlike Huntington's disease, healthy living will greatly reduce the risk of developing this disease. For this and other genetic diseases that there are opportunities to prevent or treat, it is less problematic for carriers of gene A to have knowledge of it. Other diseases are recessive, ie both alleles must have gene defects for the disease to break out. As mentioned, 5% of all cancers in the breast, prostate, ovaries and colon and rectum are due to a mutated allele being inherited. The likelihood of the healthy allele in at least one cell mutating in the loop of life is high. Hereditary breast and ovarian cancer are two cancers for which gene tests are done. There are mainly mutations * two genes that can cause disease. Because hereditary diseases occur in specific families, it is possible in such cases to test healthy individuals to determine if they are carriers of alleles with mutations. The tests may indicate something about the risk of developing a disease in the future. so that cancer precursors can be detected early. Ovarian cancer can be prevented in women at high risk of developing the disease by removing the ovaries after giving birth to the children they want. Breast cancer can be cured by early diagnosis and treatment. For other recessive genetic diseases it is a prerequisite for disease progression that the mutated allele is inherited from both parents. Gene testing by healthy individuals can reveal whether you are the carrier of the gene defect. There- As two carriers get together, the risk is 25% for the child to become ill. Knowledge of this can affect the desire to have children. In any case, knowledge of increased risk or a desire to know nothing about the risk will present difficult ethical issues for those affected.

Incomplete dominance

Some genes are not inherited dominant / recessive, but as an intermediate inheritance, a middle-in-between »inheritance. The offspring phenotype is a mixture of parents' phenotypes. This is incomplete domination. An example: The cross between a red-flowered and a white-flowered lioness gives offspring with pink flowers. This is because the flowers of the heterozygote have less pigment than the flowers of the red homozygote. At such crossings we use only capital letters: RR for the genotype red flowers and HH for the genotype white flower color. A plant with pink flowers has the genotype RH. If F1 is crossed, we get offspring with both parents' phenotypes and the intermediate form. The inheritance of the flower color of the lioness plant is red, pink or white flower. The root flower allele does not dominate over the white flower allele, and a mixture of red and white flower is expressed.

Food provides building blocks and energy

There are building blocks in all food. Our food comes from autotrophic and hot. heterotrophic organisms. In a balanced diet we usually find both plant and animal. Both in vegetables, fruits and meat there are proteins, fat carbohydrates. Our diet may well consist of only plants, but if we are to survive with an intake based only on plants, we must have knowledge so that we can put together a varied and correct amount of different plants. Food also provides energy. When the large organic molecules in the food break down, large amounts of energy are released. In the cell breath, the energy is either released as heat, transferred to other molecules or used to perform work. In all organisms, proteins can be broken down into amino acids, fat can be broken down into fatty acids and glycerol, and large carbohydrates can be broken down into monosaccharides, e.g. glucose (see table at the back of the book). All of these substances can participate in the partial reactions in both aerobic and anaerobic cell respiration. When cell respiration takes place, the energy is "overloaded" in short-term storage before it is possibly released as heat, transferred to other molecules or used for work. The most common short-term stores in cell respiration are three different compounds: ATP (adenosine triphosphate) NADH (nicotinamide adenine dinucleotide) FADH, (flavin adenine dinucleotide).

RNA splicing

While genes in bacteria contain contiguous regions that encode proteins, most eukaryotic genes are split into several parts that do not encode any protein. The parts that encode a protein are called exons, while the non-coding parts are called introns. When pre-mRNA is formed, it contains both exons and introns. Before the mRNA is complete, ie ready for translation to protein, the introns must be removed. It happens in a process called RNA splicing. All introns of mRNA in eukaryotic cells begin with GU and end with AG. The ends of the introns are recognized by enzymes we call splice isosomes. The splice isosomes cut the introns out of the pre-mRNA. Then the exons are glued together so that the mRNA contains a coherent code. Finished mRNA is then transported into the eukaryotic cells from the nucleus of the cytoplasm, ready to be translated into protein. It is important that the cutting and splicing is accurate. An error due to an extra or a missing nucleotide will cause the mRNA to not translate to the correct protein. While the average size of a pre-mRNA in eukaryotes is 8000 nucleotides, the average size of a finished mRNA is 1500 nucleotides.

Meiosis

1 fero cellular organisms are meiosis (reduction sharing) the process that leads to the production of sperm cells, ie egg cells and sperm cells. With net reproduction, new diploid individuals emerge from the egg and sperm that fuse during fertilization. The germ cells have one set of chromosomes. Such haploid germ cells are also called gametes and include both egg cell and sperm. If the sensory cells had a double set of crowns such as the body cells, the chromosome number in the cells would have decayed for each generation. This is avoided by the fact that diploid stem cells in the known organs produce germ cells at the meiosis. In Chapter 7 we look at stem cells more. As in mitosis, the cell's DNA is copied before the meiosis begins. Therefore, the diploid stem cells also have paired homologous chromosomes where each chromosome consists of two sister chromatids. The four innate matids from each chromosome pair are distributed in the meiosis to four haploid daughter cells. The meiosis consists of several steps beyond the mitosis, and two cell divisions occur (see the figure on the next page). As the figure shows, homologous chromosomes settle in Prophase I adjacent to each other for their entire length. If DNA pieces are broken at the same location in two sister chromatids, the pieces can swap space. This is what we call overcrossing, and it provides increased genetic variation in the germ cells. On average, there are approx. 50 crossings during a meiosis in a human cell. In chapter 6 you can read more about crossover. In the meiosis, a diploid mother cell gives rise to four haploid daughter cells. In men, this results in four sperm, all of which are formed from one diploid stem cell in the testes. Meiosis occurs in many cells at the same time. In women, meiosis occurs only once a month, and only one of the haploid cells produces an egg cell that matures and loosens during ovulation. The other three haploid cells are adjacent to the cell that is to become the egg cell. They eventually perish. A human with 46 chromosomes (23 pairs) has 223 = 8,388,608 different combinations for germ cells. In addition, overcrossing in the meiosis will provide further variation. The four (2 ') combination possibilities for two homologous chromosome pairs are shown in the figure to the left.

Enzymes are biological catalysts

A catalyst is an accelerator that helps in a reaction without being used up. An enzyme acts as a biological catalyst. Most enzymes affect only one particular chemical reaction. In a human cell there are thousands of different enzymes. The activation energy needed to initiate a reaction is lower with enzyme than without enzyme, and therefore the reaction proceeds faster when enzyme is present. Enzymes are necessary for reactions to proceed sufficiently quickly at relatively low temperatures. Most chemical reactions in living organisms occur at temperatures in the range of 0-45 ° C. Our body temperature is approx. 37.5 C, and our enzymes therefore work best at that temperature. Other organisms have enzymes that work best at completely different temperatures, e.g. lives several species of arcs in the hot spring in Iceland, where the temperature may be up to the boiling point of water. There, the enzymes may need a temperature of more than 80 "C to begin working.

Use of energy in ATP

ATP is the most important energy carrier in the short-term energy storage. ATP is found in all living cells of all organisms. ATP is built up and broken down continuously in metabolism, at a high rate. The energy from this short term. the storage is quickly transferred to other forms of energy. The energy that is transferred when ATP is involved in reactions uses the organisms mainly for three purposes: mechanical work, transport work and chemical work. The table at the top of the next page shows examples of what the released energy is used for. When you eat food and burn it by cell respiration, many ATP molecules are formed in the mitochondria, which are the energy-producing organelles in the cells, ATP can be transported from the mitochondria to other organelles in the cell or to other cells in need of energy.

Long-term energy stocks

ATP, NADH, NADPH and FADH are short-term energy stocks. Energy is stored and used at high speed. All living organisms must also have long-term storage of energy. Long-term stocks are energy reserves that we can use when short-term stocks are empty. Long-term stocks are not as readily available as short-term stocks. Several stages of degradation processes are needed to release energy from long-term storage. The long-term stores in our body consist mainly of carbohydrates, fat and some protein. If you fill a wood stove full of energy-rich wood cubes, everything will burn up, and the stove will get hot as the temperature rises in the room where the stove is. Fortunately, this does not happen to living organisms that eat energy-rich foods. Our body temperature is regulated and it stays as constant as possible. We humans can burn just enough to keep the temperature at about 37 C, and we burn more when we are active than when we are at rest. We have regulatory mechanisms that ensure that surplus energy can be stored in a long-term storage. We can collect this surplus and convert it into short-term storage when we need energy. The regulatory mechanisms consist of an interaction and collaboration between the DNA, enzymes, hormones and nerve cells. In the liver and in the muscles, humans have long-term stocks of eriergi as of about 250 g of the carbohydrate glycogen. When the glycogen stores are lull, the body will not increase the combustion, but it uses the excess energy bestowing molecules. In a person who does not exercise, the excess energy is used to add up a long-term supply of fat. In a person who exercises a part, reactions in which fat molecules or protein are formed in special cells, the body also forms energy stores of proteins. Much of the excess of the amount (and thus muscle mass) of the muscles increases. Also, a person's energy is used in reactions where proteins are formed, and so that a protein that exercises a lot can increase the amount of fat in the body if the energy intake is high enough. A person who consumes food with more energy than the body needs to maintain the ability to work and to maintain body temperature, build up a long-term storage, and increase weight. A person who consumes less food than the body needs will first start using the glycogen storage, then the fat and finally the proteins - all this to get enough energy-rich compounds for cellular respiration. Then the weight decreases. When large organic compounds such as carbohydrates, fats and proteins are cleaved by cellular respiration, the reaction gives energy. The text on food packages indicates how much energy the food contains, and the amount of energy is given in an international standard unit (SI unit) called joule, abbreviated J. Nevertheless, many still use the old unit of calorie (1 calorie). = 4.2 J) when talking about the energy content of food. The energy content of food is a measure of how much energy can be released when the substances in the food are involved in chemical reactions where large organic compounds break down into smaller and simpler end products.

Abnormal chromosome

Abnormal chromosome numbers are incorrectly distributed so that one pitcher cell gets two, while the other cell does not get any of the homologous chromosomes in ct pairs. ulcerating serious negative chance sequences Most cases where a ruptured egg cell has an abnormal number of chromosomes, leads to spontaneous abortion 1 In some cases, ouan adttowou ey auapipu sapay 8o sapan aranso paepru chromosome pair Three editions (chromosome) of chromosome 21 are not fatal, but give Douma syndrome These individuals have 47 chromosomes in all cells. Ca, an ay 700 is born with Down syndrome. The condition can be detected by amniotic fluid samples the chromosomes are examined. Also, an early ultrasound examination (around weeks 11-12) can detect Down's syndrome. During this period of pregnancy, a characteristic skin fold appears in the neck of the fetus if it has the syndrome. Girls who have only one sex chromosome (written XO) have Turner's syndrome: Such girls have 45 chromosomes in all cells. They are short-grown and previously did not develop secondary sex traits. Thanks to the use of growth and sex hormones, some of the symptoms can be treated, but ovaries do not develop, so such girls are usually sterile. This syndrome has no bearing on intelligence. Tumor syndrome is the only syndrome in which the fetus survives with only 45 chromosomes.

Cell division - mitosis and meiosis

All cells come from cells. This happens by dividing a mother cell into two daughter cells. When single-celled organisms, for example, bacteria or single-celled algae and animals, divide, the entire organism is reproduced by a two-line of the cell. As you read in the previous section, the division phase constitutes a minor valley of the cell cycle, and can only start when the cell has copied its DNA and has two identical genomes (see page 144) or chromosome sets. The deline phase consists of two parts: first the two chromosome sets are separated, then a two-partition of the cytoplasm is separated and the mother cell is divided into two daughter cells. In multicellular organisms, cell division means that adult organisms can develop from one fertilized egg cell, that old cells can be replaced, and that diseased or damaged organs can be repaired. Both skin cells and blood cells are replaced daily in large quantities. This is a form of cell division called mitosis. Cell division is also required for germ cell formation in both single-cell and multicellular eukaryotes. This form of cell division is called meiosis. It is the way the chromosomes in the cell nucleus are distributed that determine whether it is mitosis or meiosis. Depending on how the chromosomes divide when the nucleus is divided, there are two main forms of cell division: • mitosis (common cell division) • meiosis (reduction division) The chromosomes are distributed differently in the nuclei of the daughter cells in mitosis and meiosis. Since prokaryotic cells do not have a nucleus, we find mitosis and meiosis only in eukaryotic cells.

Gene regulation

All cells in both single-celled and multi-celled organisms participate in different biological processes at different times. Each cell therefore needs different active proteins at different times. Therefore, different genes are expressed, that is, which are translated into protein, in the different cells. That gene expression is controlled by controlled processes is called gene regulation. In multicellular organisms, it is particularly evident that gene regulation is an important process. In humans, gene regulation causes the fertilized egg cell to give rise to approx. 200 different cell types. Since all cells (with few exceptions) in an organism contain the same genes, the difference between a nerve cell and a skin cell is that through gene regulation there are different genes that are expressed in the two cell types. Cells of a given cell type are also able to interact with other cells and respond to signals coming from the environment outside the cell. In many cases, such communication will cause specific genes to be expressed, and the cell may become active in specific biological processes. When some years ago, scientists replaced the cell nucleus of a frog's egg with the nucleus of a frog's skin cell, it became clear that all the different cells in multicellular organisms contain the same genes. The result of the experiment was a normal embryo that gave rise to a rumen troll with all organs in place. Thus, the skin cell may not have lost any important genes. The same principle has also been demonstrated for mammals, and we already know that cells from specific parts of the plant can be dissolved into single cells that can give rise to fully developed plants. These are examples of cloning of individuals, where the whole organism's genetic material is copied into the new individuals. It is the combination of the genes expressed as RNA and proteins that determines which cell type is formed when the cell is differentiated. The genes a cell expresses depend on both the cell's past and the environment it currently has. When a cell is differentiated, gene expression is maintained throughout the following cell generation. We can say that cells have memory. We do not yet know enough about the different cell types that we can say exactly which genes or proteins are expressed in each cell, but we know the following: Many processes are common to all cells. Examples include cellular respiration, transcription and protein synthesis, and processes involving the cytoskeleton. Different cells will therefore have many proteins in common. This applies to, among other things, RNA polymerases, proteins in the ribosomes, enzymes involved in metabolism, and proteins in the cytoskeleton (cell skeleton). The cytoskeleton is a network of protein fibers that support the cell internally and hold other organelles in place. Genes that encode such proteins that are involved in basic processes are often called household genes. Household genes are always expressed because they encode the proteins the cell constantly needs. In the cell cycle (see page 141), there are several checkpoints that ensure that the different stages of the cycle arrive at the right time. Cyclins are a group of proteins that control cell development throughout the cell cycle. Different cyclins are expressed at different stages of the cell cycle and ensure that the cell comes through the cycle. Thus, genes encoding the different cycles are expressed in all cells that are in the cell cycle. A typical human cell expresses 10,000-20,000 of its ca. 23,000 genes. The number of mRNA molecules produced from each gene varies with the cell type. Highly specialized cells, e.g. muscle cells, express a smaller proportion of the genes - from 3 to 5%, Some proteins are produced much of it in specific specialized cell types, while not found in other cell types. An example of this is hemogiobin. We only have hemoglobin in the red blood cells. It is absolutely necessary for the binding of oxygen and the transport of it to the cells of the body. Mature red blood cells are so specialized for this task that they have no need to produce proteins for other tasks. Therefore, the nucleus of red blood cells is broken down. But before the red blood cells mature, large amounts of mRNA that encode hemoglobin are produced. Another example of specialized cells is plasma cells, which are highly specialized B lymphocytes. Each such cell produces large amounts of anti- play an important role in our immune system. You can read more about drugs and B lymphocytes in Bios biology 1. Another example: In all cells we have a gene for the hormone insulin. But this hormone is only made in a few and very specialized cells. Insulin is made in a cell group in the pancreas called the Langerhans Islands. The hormone is thus secreted from these cells. It is necessary for regulating the body's metabolism of carbohydrates and fat. Insulin allows cells in the liver, muscle and adipose tissue to absorb glucose from the blood. Deficiency of insulin leads to diabetes.

Reprogramming of cells

All cells in the body contain the same genetic material. Which genes are turned on and expressed, and which ones are turned off, then determines which cell type the cell develops into. For example, there are three genes that are variously turned on and off in blood cells, respectively, many -uny skin cells. 80 As mentioned earlier, pluripotent stem cells are particularly interesting because of their ability to give rise to all cells in the body. Therefore, several researchers have begun the very extensive job of identifying which genes determine that a few cells just turn into pluripotent stem cells. The aim of this research is to understand what differentiates ordinary cells from pluripotent stem cells. It is hoped that this knowledge will enable different cell types to be manipulated so that they can be reprogrammed into pluripotent stem cells. If it proves possible, it is possible to obtain pluripotent cells that can be used in research 05 treatment, without using embryos or fetuses. A research group from Japan reported in 2006 that a combination of only four genes could reprogram normal skin cells from mice to pluripotent stem cells. (You can read more about this work in the extra material on the next page. Such cells are called iPSC (stands for induced pluripotent stem cells). These were startling results, and many choices. These results have now been confirmed by a large number of other researchers - skeptical of fun groups. The same has now been done with human skin cells reprogramming the skin cells, researchers use genetically modified retroviruses to get the genes into the skin cells. Retroviruses act in that when they infect a cell, parts of the virus's genetic material are inserted into the cell's genetic material. This means that the cell starts to produce proteins according to a recipe from the Researchers in recent years have developed simpler methods than using retroviruses to reprogram the cells. Today, iPSC cells are made from patients with a variety of conditions / diseases . Examples are Rett's disease, fragile X syndrome, Angelman's syndrome and Prader-Willys syndrome. You can read more about these diseases on the Bios website. The advantage of pluripotent stem cells from these patients is that we can study the development of the conditions / diseases in laboratories and laboratory animals and understand the development far better than if we only examine patients with these conditions. This can lead to faster treatment of new treatment methods for these patient groups. the genes that the virus has transmitted to the cell.

Cell cycle

All cells that have cell division during mitosis go through a cell cycle. We shall first look at the different stages of the cell cycle. We will return to cell division in the next section. In eukaryotic organisms, the cycle consists of the cells passing through controlled stages from the onset of cell division and until they divide. The stages are repeated for each split, which is why we call it a cycle. The cell cycle mainly has two phases: the interphase and the division phase. The interphase accounts for 90% of the cell cycle. It is the period when the cell grows by producing proteins and cell organelles. This takes place throughout the interphase. DNA is only copied in part of the interphase in what we call the S phase (synthesis phase). How long the cell cycle lasts is different for different cells. In most human body cells, a cell cycle lasts for about 24 hours, and the interphase is 23 hours of this. Half of the interphase is for DNA copying (the S phase). The sharing phase takes approx. one hour. In the division phase, a mother cell is divided into two daughter cells. The figure next to it shows an example of the cell cycle in the root cell of a plant. This entire cycle takes a total of 18 hours, and DNA copying takes 11 of these 18 hours. The cell cycle is under strict control. This check ensures that the different stages of the cycle occur at the right time and in the correct order and only once per cell cycle. The control determines how quickly different cell types divide. While, for example, skin cells, intestinal cells, and bone marrow cells divide throughout life, liver cells have an opportunity to divide as needed, and photosensitive cells in the eye and nerve cells do not divide after they are fully specialized. To control which cells to divide when, the cell has specific control points where the cell cycle stops. The cell must then receive a ready signal to proceed in the cycle. The most important checkpoint is in the interphase, before the copying of the DNA begins. If the cell receives a clear signal here, it will normally complete the entire cell cycle and divide. If no clear signal is given, it will exit the cell cycle and into a state where it does not divide. The vast majority of cells in the body are in this state. Signals from both outside and inside the cell can affect the control points. Cancer cells can escape the control points in the cell cycle and therefore have uncontrolled growth.

How the enzymes are named

All chemical compounds have names. Most enzyme names end in -ase. Many of the enzymes have names that say something about the specific reaction they catalyze. It has proved to be an appropriate way to name them. An example is phosphatase, which helps to transfer phosphate groups between molecules. Other names say more about the substrate than about the reaction. Lactase catalyzes the reaction in which lactose, milk sugar, is converted to monosaccharides glucose and galactose. ATPases are a large group of enzymes that catalyze reactions in which ATP (see page 62) reacts with water to form ADP, a phosphate group and released energy or vice versa when ATP is made. ATP ashes are found in membranes, helping to pump ions through the membranes to create gradients. Examples are H ions in chloroplastic and mitochondrial membranes and Na and K * ions in the cell membrane of nerve cells. Some enzymes have names by the place where they exist. Special organelles, lysosomes, in animal cells and some protist cells we call the "reindeer husbandry" or "suicide organ or". This is because they contain the enzyme lysozyme, which breaks down organelles and cells. In this way, cells with lysosomes can digest bacteria, or they can release the enzymes in their own cytoplasm and thus destroy themselves. An example is when white blood cells can eat bacteria and digest the contents by means of lysozyme. Another example is that cells must constantly break down during fetal development in animals. At a certain stage of fetal development in humans, we have skin between what is supposed to be the individual fingers, and lysosomes in these skin cells produce lysozyme that dissolves and removes this skin. Another example: The enzyme papain is found in the fruit papaya. This fruit can be used to thaw meat that we think is too chewy. If we cut papaya into thin slices and put them on the meat, enzyme from the fruit will break down protein fibers in the meat and make it darker. Quite a few use contact lenses, and the contact lenses need to be cleaned in lens fluid. Contact lens fluid contains, among other things, the enzyme papain, which breaks down tiny protein fibers from the cornea and inside the eyelid of the lens wearer and from bacteria that can linger on the lenses during the day.

Genetic fingerprint

All people have unique fingerprints. Fingerprints can thus be used to distinguish between individuals. Similarly, there are genetic differences between individuals of humans and similarly in all other species of animals. A technique used to distinguish individuals of the same ancestry based on genetic differences is called "genetic fingerprints. Other names of this technique are DNA testing, DNA typing and DNA profile ring. In forensic medicine, it is common to use genetic fingerprints. Usually these are paternal cases or the use of biological material such as Genetic Fingerprints With few exceptions, all individuals of humans and of other species are genetically different. Among the exceptions are species that propagate unfamiliar, evidence in criminal cases. e. bacteria or plants that form new individuals vegetatively by outliers, and solitary twins in species that reproduce sex. As we discussed in Chapter 5, the individual differences are largely due to processes in the meiosis. In addition, all DNA is subject to mutations While the genes must be kept as intact as possible so as not to lose their function, the DNA in the regions between the genes can change a lot without causing any negative consequences. In the regions between the genes, there are short, repetitive DNA sequences (with two to five bases), and it is especially in these regions that we find great variation from individual to individual. The short DNA sequences vary in number from person to person, so the length of the repeated areas varies. This can be used in forensics to identify individuals and make DNA a suitable means of proof in criminal cases, the DNA analysis takes place in several steps. First, DNA must be extracted from biological material. In criminal cases, there can often be a very limited number of cells, e.g. from hairs or blood residue. Subsequently, parts of the DNA are copied by polymerase chain reaction (PCR). In addition, PCR is run on the sex chromosomes. The overall result of the analysis for one individual is called a genetic fingerprint or a DNA profile. by the suspects or from others who have not been identified. Since the genetic fingerprints from the biological material are identical to the imprint of one of the suspects, that is, the DNA originates from this person. The probative value depends on the case. When there is no correlation between the suspect's genetic fingerprint and the biological trace, DNA analysis can be used to acquit a person. A collection of genetic fingerprints from many people is called a DNA register. Such a register makes it possible to compare genetic fingerprints from a scene with the genetic fingerprints of previously punished persons. Norway has a DNA register that was launched in 1999 and is operated by "Kripos. Comparison of genetic fingerprints can, as mentioned, be used to investigate relationships between people, e.g. in paternity cases. Because a child has chromosomes from both parents, it will have some repeated DNA sequences from mother and others from father. Those parts of the genetic fingerprint that do not originate from the mother must come from the father. If it is not possible to obtain DNA from father, DNA from his parents can provide answers. Using PCR to create genetic fingerprints is an inexpensive and sensitive method. Previous methods made stricter requirements for DNA quality. Using PCR, it is possible to obtain safe responses from DNA that is not intact, or from as little biological material as one strand of hair. For the results to be sufficiently secure, good routines and high accuracy are required in a large work where analysis can take several days. It is important for legal certainty that the analysis is as thorough as possible.

ATP structure and mode of action

An ATP molecule is made up of the base adenine, which is bound to the monosaccharide ribose Adenin is a base because it can bind H-tones. The ribose is bound to a chain of three phosphate groups or phosphate ions. Adenine plus ribose we call adenosine, and together with the three (T stands for tri-) phosphations, the ATP is called adenosine triphosphate. The phosphate has chemically normal HPO, but we write this ion abbreviated as the letter P. The figure next shows both a simplified model and the structural formula for the ATP molecule. ATP is a "wonder molecule" that all living organisms depend on. All living organisms can make ATP, and they use this molecule to capture and transmit energy. Using an ATP-ase enzyme, ATP can be cleaved to ADP, adenosine diphosphate, and a phosphate group. The binding in ATP is unstable and is therefore easily broken. It is a common misconception that energy is stored in the bonds between the phosphate molecules in ATP. It does not. P is easily detached from ATP, and the result is ADP. A phosphate is transferred to another molecule, and this molecule then gets increased chemical energy. This increased energy is necessary to be able to enter into further reactions. The amount of chemical energy that is transferred to another molecule when a phosphate group is added is not large, but each cell contains an enormous number of ATP molecules, so that the sum of the energy becomes large. When a phosphate group is released from ATP, the compound has only two phosphate groups remaining. Then we call the ADP, where D stands for di, which means two. When P becomes detached from ATP, then the phosphate group is transferred to another molecule, which thus becomes more energy-rich. Furthermore, this energy is used for transport through cell membranes, for reactions where new and often larger compounds are formed, or for movement. Some of the energy from cleavage of ATP is eventually released as heat. A marathon runner needs the energy of about 2 kg of ATP per minute. Part of the energy goes to motion, and a lot of energy is released as heat. ATP axis is required when P is cleaved from ATP. The ATP axis acts on now when the reaction goes the other way, ie when ADP and P are built together into ATP. In the digestive system, the large molecules in the food we eat are broken down into smaller molecules. This provides building blocks for the body and releases energy that is used, among other things, for the active transport of substances, for heat or to rebuild ATP by ADP and P. Reuse of ATP is crucial, for the amount of ATP needed by the body in the course of one day. equals about your body weight! The other phosphate group in ADP can also be split off, and then we get MP, where M stands for mono, which means one. This occurs less frequently, and the amount of energy transmitted when ADP is cleaved to AMP is small.

Resistance to pesticides

As an example of possible negative consequences, we will look more closely at the cultivation of GMO plants that are resistant to glyphosate. Glyphosate works in many plant species, but it has only been used to a limited extent in fields because it also kills the plants that are grown. If farmers grow GMO plants that are resistant to glyphosate, they can in principle reduce the total amount of pesticides because there are several types of selective pesticides they do not need. But because the resistant culture plants tolerate this herbicide, glyphosate to be sure that they will kill all the weeds, here there is a risk of an undesirable indirect effect due to changed cultivation practices. In Norway, in 2012, an application to market a glyphosate was rejected, enabling farmers to use an even more resistant version of the plant species of oilseed rape, partly because the oilseed rape in Norway has wild relatives that can become resistant, e.g. . åkerkål. Field cabbage is a species that grows as weeds in fields. That ability as the last gene. Another example that can be mentioned is genetically modified plants with a bacterial gene that produces an insecticide. If such plants are grown near wild relatives, pollination of the wild species may occur and then wild species may become insect resistant. The toxin that the cabbage has to cope with would have been enhanced by the transfer of glyphosate wood. produced in the GMO plants (and possibly in their wild relatives) will furthermore be toxic to beneficial insects or species with important ecological functions. Ex pollination On the basis of a large selecium press, insects are also likely to develop resistance to the poison Pesticides. clays based on this insecticide will therefore no longer be effective, creating a need for the use of more pesticides or even more toxic agents, which has clearly negative effects on the environment around the fields. As we see, genetically modified plants can cause problems in agriculture and in nature. However, the extent to which they genetically modified a more problematic one in nature than other breeding or introduced species is more unclear and far-reaching depending on the characteristics of the individual species and the environment in which it is exposed. For example, we see that salmon farmed salmon that are not genetically modified, has already to a large extent mixed with many wild populations in Norway. If GMO salmon with worm genes increases growth and cold tolerance is used in Norwegian aquaculture, it will be able to outcompete the wild stocks in the course of a few generations.

Pluripotent and multipotent stem cells

As mentioned, there are several different types of stem cells. Regardless of where they are isolated from, they are often divided into two main types of pluripotent and multipotent star cells. Pluripotent stem cells are characterized in that they can give rise to all cell types in a born individual. "Pluris come from Latin and can mean multiple. Pluripotent stem cells have been found by researchers in embryos and aborted fetuses. If an egg cell is hatched in the laboratory, the fertilized egg can be used to isolate pluripotent stem cells. Five to six days after fertilization, the egg has split a number of times and developed into an embryo, which at this stage is called a blastocyst. A blastocyst is like a hollow ball and consists of about 100 cells. The walls of this "ball" consist of cells that later develop into the placenta and the membranes around the fetus. Inside the "ball" are a few pluripotent stem cells that will produce the cells that eventually form the entire new individual. Pluripotent stem cells that are isolated from a blastocyst are often called embryonal stem cells because they originate from an embryo. Pluripotent stem cells have also been found in 5-9 week-old aborted fetuses. They are often called fetal pluripotent stem cells. These stem cells can be isolated from the part of the fetus that will later produce the germ cells. The use of embryos in research is ethically very contentious. The embryos are destroyed when the stem cells are removed. The embryos that are usually used in such cases have been left over after test tube fertilization, where the goal is to have children. An embryo is human life at its earliest stage. Because embryos have the potential to be born to humans, many believe that they should not be used in research. Others believe that excess embryos can be used if the purpose is very good. Research that satisfies high ethical requirements can be such a purpose. because abortion itself is contentious. When using both embryos and aborted fetuses, the woman / couple will be in a difficult situation by being asked to contribute to research. Because of the ethical challenges, many hope to find other sources of pluripotent stem cells, sources that do not involve the use of ethically questionable sources or methods. The use of aborted fetuses is also disputed, and it is ethically problematic. Multipotent stem cells differ from pluripotent stem cells in that they can only produce a limited number of different cell types and not all cells in an individual. Multipotent stem cells are also often called adult stem cells or estrogen cells from born individuals to show where they are isolated.

DNA Isolation

As you read about in biology 1, cells are made up of a variety of molecules. laughing. The most important main groups are proteins, lipids (fats), carbohydrates and the nucleic acids DNA and RNA, (You can read more about these molecules on the Bios website) When we work with the DNA, e.g. When deciding the base sequence (sequencing), conducting DNA analyzes, cloning, etc., it is important that the DNA is sufficiently pure. Therefore, there is a need to isolate the DNA from the other molecules. Isolation and purification of DNA is a standard procedure in laboratories where it is routine to work with DNA. The starting point is cells from the organism to be examined. Blood is often used from humans. If they are tissue pieces, we first crush them to separate the cells. If the DNA is made available, the cells are destroyed. It happens through physical and chemical destruction. Then, RNA is removed by adding an enzyme. The DNA is then centrifuged in a tube with an alcohol solution. Then the DNA will collect at the bottom of the solution. The DNA can then be extracted and isolated.

In illness, enzymes can leak from cells and tissues

Based on the measurement of the amount of enzymes in blood plasma, unin and other body fluids, the doctor can make a diagnosis. The methods for measuring enzymes in body fluids are relatively simple. Some enzymes are produced in all cells, e.g. catalase. Other enzymes are only produced by certain tissue types, e.g. pepsin in the stomach and trypsin in the small intestine. In body fluids, e.g. urine, there is normally a small amount of enzymes that are produced in special cells elsewhere in the body to participate as catalysts there. Sometimes such enzymes can leak out of the cells. In particular, it will leak a little from cells in the muscle, liver and blood, because these cells have a powerful metabolism with many different enzymes in activity. In disease, cells can leak out of too much of one or more enzymes. Enzymes leak out, for example, into the blood, and are then taken up into the kidneys. Therefore, an examination of the urine may reveal illness. The amount of enzymes and their type may indicate how serious the damage is. Blood tests can also reveal illness. In some liver diseases, the amount of special liver enzymes in the blood will increase, and disease can then be detected with a simple blood test. For example, enzymes will leak when there are infections in the bile ducts, when there is hepatic infection in the liver, and in beginning cirrhosis. Some heart disease caused by damage to the heart muscle cells causes the amount of enzyme produced in the heart muscle cells to increase. If this enzyme occurs in very large quantities, it indicates myocardial infarction.

Biotechnology and Gene Technology

Biology can be defined as, all technological sum uses living organisms or cells of living ores to tramplify products, Genmodi. with certain characteristics belong to this defi. fissured organics Jogt includes eco-methods for the production of al, wine and fire using yeasts and the production of, for example, antibiotics and industrial chemicals. Biological treatment of sewage and treated bacteria, nutrients sam oit, yoghurt o Hojeynp ninion and sapun uui esto Jaoy afjonds syy nae youaly ysuto se of years used microorganisms in the production of food. We therefore often distinguish between traditional and modern biotechnology. The starting point for traditional biotechnology is living organisms and cells where the genetic material has not been altered by modern biotechnology. Modern biotechnology, genetic engineering, uses organisms or cells and examines or modifies the genetic material using various techniques. for such organisms is GMO. Gene technology makes it possible to assemble DNA in new ways and transfer DNA between organisms and species. For example, the organism can have extra genes, genes can be changed, and parts of genes or whole genes can be removed. The way in which DNA from different species is put together is called recombinant DNA technology. A more popular word for the same is gene splicing. The purpose is often to obtain new, beneficial properties of an organism. When GMO is used to produce food products, these food products are often referred to as genetically modified foods. In Norway, all activities related to biotechnology and / or the genetic standard are closely regulated by legislation, first and foremost. the Biotechnology Act and the Gene Technology Act. You can read more about these laws on the Bios website.

Obesity

Body weight is 70% genetically determined and 30% controlled by the environment. In individuals with early-onset severe obesity, 7% have a single-point DNA mutation. Most cases come from multiple genes, and we know of five genes where mutations can cause extreme obesity. One such gene encodes leptin, which is a hormone that provides the brain with satiety. Individuals with mutation in this gene never get saturated, no matter how much they eat. A prerequisite for the genetic defect to lead to obesity is that there is adequate access to food. Therefore, it is the interaction between heritage and the environment, ie the lifestyle, that leads to overweight. When we have a lifestyle with physical activity and a healthy diet, the expression of genetic obesity may be reduced or prevented from being expressed. Children with mutated leptin gene can be treated with active leptin. It provides reduced appetite and normalized body weight. Treatment of other forms of extreme obesity is more complicated. The reason for a general weight gain in the population, i.a. In many western countries, lifestyle and environment are not changes in genes.

Stem cells and cancer

Cancer is caused by the inheritance of a cell changing so that the cell loses important control mechanisms (see Chapter 5). It may be, for example, that cancer cell. ne grow faster than normal cells, that they grow in the wrong places, or that they are not there as fast. In order for a cell to become a cancer cell, mutations must normally occur that cause errors in several genes. Such gene defects rarely occur, stem cells and cancer and, in the main, there are long-lived cells that can turn into cancer cells. Stem cells are among the cell types in the body that live long enough to get the genetic defects needed to develop cancer. Recent research has shown that several cancers are probably due to genetic defects that occur precisely in the stem cells so that we get a cancer stem cell. Cancer stem cells and normal stem cells often have many of the same molecules on the cell surface. This can make it difficult to distinguish between them. So much of today's research in this field is about finding bun that separates them, so that we can come up with new ways to remove the cancer cells. Today, you believe that removing the cancer stem cells will cause cancer. wasting itself, because it is probably only the cancerous stem cells that can create. keep the production of cancer cells over time - just as regular stem cells are needed to keep the production of normal cells going. While common cancer cells are characterized by dividing frequently, cancer stem cells rarely divide. This is unfortunate when it comes to treating cancer. Much of today's cancer treatment (radioactive radiation and chemotherapy) is about killing rapidly dividing cells. Therefore, cancer stem cells will be less damaged by this treatment than other cancer cells. You can often see a clear reduction in the size of a tumor after treatment, but the most dangerous cells - the cancer stem cells - can be difficult to remove with such treatment. The problems with killing the cancer stem cells could possibly explain where. for some cancer patients relapse after the cancer appears to be gone after a cancer treatment. While the treatment has killed the mature cancer cells, any remaining cancer stem cells could again cause cancer. On page 140 you could read about telomeres that we find at the end of all chromosomes in eukaryotic cells. In most of the body's telomeres, the telomeres become slightly shorter for each cell division and function in a way like a "clip card. When the clip card is empty, the cell will no longer be able to divide, and the cell there. Shortening the telomeres is one of the body's mechanisms to prevent cells dividing r many times. Stem cells, which are naturally long-lived, produce the enzyme telomerase. This ensures that the telomeres do not become shorter for each cell division. This also applies to cancer stem cells.

Cancer

Cancer is the common term for a number of diseases where the characteristic is uncontrolled cell growth. Many different cell types can be the starting point for such diseases. The cause of cancer is mutated genes that are involved in the cell cycle and which cause the cells to escape control cancer. Cancer canisms that normally restrict their growth. There are two genes that directly contribute to cancer: tumor-suppressor genes and oncogenes. Tumor supressor genes usually act as inhibitors of cell growth. Normal activity in these genes prevents cell growth from proliferating. major types of mutated tumor-suppressor genes make the brake not work, and the cells can then grow and divide unrestrained. A mutant tumor suppressor gene is recessive because a normal allele will provide normal function. Oncogenes normally encode proteins that stimulate normal cell growth and division. If a mutation either increases the amount of protein that such a gene produces, or the activity of each molecule formed, oncogenes can cause cancer. Such mutations are dominant. In addition, damage to repair genes will contribute to the development of cancer because other damaged genes are not repaired. Of all cancers, 80-90% of changes, ie mutations, are due to the dye during life and are not inherited. Of all cancers in the breast, prostate, ovaries and colon and rectum, 5% is inherited from a mutated gene. The most common hereditary cancers are breast / ovarian and colon / uterine cancers. Inherited mutations have also been found from cancers of the kidneys, skin and skeletons. If cancer is to develop in a cell, both alleles in the gene in question must often be mutated. If a mutation is inherited, all cells of an individual will have the same mutation. Then, one allele of the gene pair is mutated in all cells. Because mutations occur spontaneously in the cells, the healthy allele is very likely to mutate into at least one cell during the individual's lifetime, making this cell develop into a cancer cell. If, on the other hand, both alleles of a gene pair are healthy at birth, the probability is very low for both alleles of a gene to mutate in the same cell. In hereditary eye cancer in children (retinoblastoma), 100,000 times more likely that an individual with an inherited mutated allele will have eye cancer than a person without mutations. For this reason, cancer disease often occurs earlier in life when a mutated gene is inherited than when it is not inherited. In many cases it is known which genes are mutated.

Cardiovascular disease

Cardiovascular disease is the most common cause of death in Norway. Since 1990, the disease has hit an ever-growing number of middle-aged people, so today, most of the time, older people die from heart attack. Infarction is called when parts of the heart muscle die due to oxygen deficiency because deposits clog the blood vessels that supply the heart with oxygen. High cholesterol is the most important risk factor when it comes to heart attack. Three out of four Norwegians today have high cholesterol levels. This is largely due to a lifestyle with high saturated fat and trans fat (see page 125). which raises blood cholesterol levels. However, cholesterol levels nationwide have dropped noticeably after 1970, which may be due to increased awareness of diet and changing margarine composition in the 1970s. Vegetable oils and omega-3 fats from fish and marine animals contain unsaturated fats that reduce the amount of cholesterol. A risk factor that cannot be affected is the innate genes. Some genes lead to hereditary high cholesterol levels and cause a condition called familial hypercholesterolemia (FH). Family hypercholesterolaemia is a dominant disease. It leads to increased levels of cholesterol in the blood and thus to an increased incidence of atherosclerosis and heart attack resulting in death. 50% of untreated men who are heterozygous for the diseased allele may expect to have cardiovascular disease before they are 50 years of age and reduce their life expectancy by 10-30 years. As many as 1 in 300 Norwegians have the mutated gene for FH. Thus, FH is the most frequent of the dominant hereditary diseases. Cholesterol-lowering medications combined with lifestyle changes can reduce the risk of developing the disease. Key words here are less saturated fat, more physical activity and smoking cessation.

Exothermic and endothermic reactions

Chemical reactions are either exothermic, ie they emit heat energy, or endothermic, ie they absorb heat energy. In metabolism, all living organisms have both build-up and degradation processes. In the process of building up, there are a number of chemical reactions that require energy. The purpose is to put together molecules so that they form other and often larger products. In decomposition processes, energy is released as the molecules react and form new and smaller compounds. Some chemical reactions that release energy are very slow; they take a long time. That's because the molecules that participate in the reaction need a certain amount of energy before the reaction can happen, even though all this energy - and more than it is released afterwards. The amount of energy needed for the reaction to start is called the activation energy or the starting energy. We can compare the activation energy with the energy we supply by burning and then releasing heat energy. First, the wood must be supplied with some energy from a match, then the wood emits large amounts of energy. It must be so that the reaction does not start until the starting energy is applied. Imagine if the wood could catch fire without lighting a match! exothermic chemical reaction with rocks. The rocks are first pushed upwards and then they roll down the large ground. The energy The figure on the left shows how we can compare the molecules in one that the person uses to push the stones upwards is the activation energy. As the stones roll down, energy is released to the surroundings. a small hill.

Chromosome mutations

Chromosome mutations result in changes in chromosomes in size and organization. Such changes tend to occur in connection with overcrossing of the meiosis. If the crossover between non-homologous chromosomes occurs, parts of one chromosome are transferred to another (see Figure page 189). Chromosome breakage can lead to four types of changes in the organization of the chromosomes. A chromosome may have a bit (deletion) A chromosome may have a bit that is repeated (duplication) A chromosome may have a bit that is reversed (inversion) (translocation)

Cloned animal health

Common to all cloning experiments is that for every seemingly well-bred animal many other animals have died during fetal development or are eating the birth due to severe malformations. Enlarged tongue, deformed head, malfunctioning kidneys, defective immune system, diabetes and unnatural posture are examples of conditions we can find in cloned animals. Many attempts are needed to get a living clone, and so far we do not know exactly what makes cloning so difficult. In the trials that resulted in Dolly, a total of 277 attempts had to be made before Dolly was born the only living clone. Living offspring is also no guarantee that the clone is healthy. Cumulina, the world's first cloned mouse, was born in Hawaii on October 3, 1997. Since then, a large number of mice have been cloned, and it has even been cloned for six generations. Cloned mice are apparently healthy, but they have a clear tendency to become overweight. However, the overweight cloned mice are offspring with normal weight. This indicates that a common gene regulation is the cause of the overweight.

Examination of Inheritance Patterns

Cross-sectional schemas we remember from Chapter 5, the homologous chromosomes separate layers in May Therefore, we can predict in relative terms the gene distributions distributed to each parent's cells. Then we set up simple cross-schematics cam showing how the germ cells from each parent can be combined into dinloid individuals. In this way, we quickly get an overview of the probability of getting the different phenotypes of the offspring. All such crossing diagrams show a probable distribution of the characteristics of the offspring, and the figures will never fully match the reality. But they are useful when studying the inheritance of one or more genes. If we look at more than two traits at once, the forms become more complicated, because the alleles for each trait can be combined in so many ways into new individuals. Once the genotypes of a parent pair are known, we can predict the probability of the genotypes of the offspring. We can also determine whether an allele is dominant or recessive when we see offspring phenotypes. Based on the relationship between the phenotypes of the offspring, it is possible to determine whether there are two genes acting on the same trait, whether a gene is located on the sex chromosomes, or whether there has been cross-breeding between homologous chromosomes. We will now look at inheritance of properties and use cross-forms for it.

From DNA to RNA Transcription

DNA contains information on how each individual cell in an organism should function. Because all cells in the body (with few exceptions) contain the same DNA, we can say that each cell contains all genetic information about the development, structure and behavior of the adult organism. In addition, of course, the environment affects the individual organism, e.g. through learned behavior The function of the DNA is thus to store in a stable form - the genetic information needed for each cell to function optimally in an organism. How, then, is this information expressed in the genetic material? How can the information stored in DNA in a fertilized egg cell lead to the development of adult well-functioning individuals of a particular species? The answer is that the genetic material controls the production of proteins that are the active molecules in the various biological and chemical processes in cells and organisms. This control is done by delimiting bits of the DNA strand, ie genes, containing the code for certain proteins that RNA consists of sugar - phosphate sugar - phosphate osy. connected one after another. The bases are connected to the sugar. RNA is a single strand, and T is replaced by U. determines the characteristics of the individual. Thousands of different proteins work in perfect interaction in healthy organisms, and there are different proteins that are active in the different cell types. Proteins can be grouped according to the different functions they have. Some examples: enzymes, transport proteins, support tissues, antibodies, movement. The DNA controls the production of the proteins through a process called gene expression. This process takes place in two steps: transcription and translation. In the transcript, for each gene, a kind of transcript is made of one of the two strands of the DNA, and it acts as a template. The transcript consists of RNA (ribonucleic acid, a nucleic acid similar to DNA, see figure on previous page). RNA from genes encoding proteins is called mRNA (messenger RNA; the m stands for English messenger). Thus, in eukaryotic cells, the recipe for proteins is transferred from the DNA in the cell nucleus to mRNA, which migrates out of the cell nucleus into the cytoplasm, where the second step takes place. In prokaryotic cells, transcription takes place in the cytoplasm. In the translation, ie the translation, the mRNA is translated into protein. You can read more about it on page 152. RNA is an abbreviation for ribonucleic acid. The name tells that it is ribose, not deoxyribose, that is sugared in the nucleotides. Three of the four bases found in DNA (A, C and G) are also present in RNA, but T is replaced by uracil (U). Unlike DNA, the RNA is single-stranded, which makes the bases of the RNA more unprotected, and the strand breaks down relatively quickly by some enzymes, RNA-ashes, that are found in the cell. Therefore, the genetic information in the RNA has limited duration. This allows the cell to send new messages from DNA via RNA. We will return to this later in the chapter. While DNA is very long molecules that make up whole chromosomes with from 50 to 250 million bases, the RNA molecules are relatively short transcripts of parts of one DNA strand. Generally, RNA molecules contain from tens to tens of thousands of bases. There are three main types of RNA: mRNA = messenger RNA (messenger in English), tags for proteins tRNA = transport RNA, carries the right amino acid to the right space in translation to protein • rRNA = ribosomal RNA, builds up the ribosomes where the translation into protein takes place. We will now look at these three types. In addition, there are various types of non-coding RNA that are likely to regulate gene expression. We do not know much about these RNA types yet. Transcription of mRNA The onset of transcription is marked by specific bases on the DNA. These bases are a promoter (= an activator, one that promotes or gets something done). The promoter also decides which of the two single DNA strands to use as template thread. Eukaryotic cells have promoters that contain the TATA bases in order. Enzymes called RNA pobyme. breeds, attach to the DNA of the promoter, open the double strand and bind RNA nucleotides that are complementary to the DNA template strand, together in a long chain. The transcription takes place in the same direction as the DNA copy. As new mRNA is created, the bonds between mRNA and DNA are broken. The DNA closes again into a double strand. In bacteria, the rate of transcription is around 50 nucleotides per second. In eukaryotic cells, the rate is 20 nucleotides per second. In bacteria, transcription stops when the RNA polymerase reaches specific base sequences in the DNA template thread, and the RNA polymerase loosens here. Then the mRNA can be translated into protein. In eukaryotic cells, transcription takes place in the cell nucleus, where pre-mRNA is formed. It must be processed into finished mRNA, which can then be translated. This processing of finished mRNA means that pre-mRNA is altered at both ends. Then, the pre-mRNA is spliced. That is, bits of pre-mRNA encoding proteins are assembled, while parts that do not encode any protein are removed.

Most organisms have DNA as an ingredient

DNA is an abbreviation of the English deoxyribouucleic acid, on Norwegian deoxyribonucleic acid. In the 1860s, some scientists managed to isolate an organic phosphate compound from the nucleus (nucleus in Latin). This organic phosphate compound reacted like an acid, so it was named nucleic acid. Since then, nucleic acid RNA has also been found. RNA is an abbreviation of the English word ribonucleic acid. So there are two kinds of nukes. Lactic Acids in Living Organisms: DNA and RNA. You can read more about RNA on page 148. Most organisms have DNA as an inheritor. Only certain groups of viruses have RNA as an inheritor. Prokaryotic organisms, which consist of cells without a cell nucleus, have most of their DNA in an annular chromosome. In addition, prokaryotic cells have smaller rings of DNA called plasmids. They contain a few genes. Eukaryotic organisms, which consist of cells with the cell nucleus, have most of the DNA present in the cell nucleus. It is divided into several linear chromosomes that look like long strands. The ingredient in the cell nuclei is protected against damage and degradation of a double core membrane. In eukaryotic organisms, the number of chromosomes varies from species to species. In addition, eukaryotic cells have small annular chromosomes in the mitochondria, and are found in chloroplasts of plants and algae. These chromosomes are more similar to prokaryotic than eukaryotic chromosomes. This common feature suggests that all organisms originate from a common single-cell origin that has evolved into the diversity of organisms found in the world today.

Nucleic acids are made up of nucleotides

DNA looks like a twisted ladder. The ladder legs are made up of two kinds of mole cool every other bucket and every other phosphate. The ladder steps consist of four fairy rabbits, one pair in each stage. We say that each step in the ladder is formed by two bases, which thus constitutes a base pair. Because each step is rotated in relation to the next, the ladder is twisted into a structure we call a double belupiral. This structure is often also referred to as each of the ladder legs issuing a single thread. When the information in the DNA is to be read or copied, the double strand is opened, and the single strand is formed double strand, where all nucleic acids (both DNA and RNA) are made up of nucleide. The pure nucleotide is composed of three parts. a sugar, a phosphate and a base, But the phosphate and the sugar are identical in each nucleotide, the base can vary according to the individual nucleotides within each DNA molecule. The nucleotides can have one of four nitrogenous bases, all of which have ring structure, in DNA this is adenine (A), cytocin (C), guanine (G) and thymine (T). The structure is quite simple and they contain only the elements carbon, oxygen, nitrogen and hydrogen. While adenine and guanine form two ring structures (called purines), cytosine and thymine form one ring structure (called pyrimidines). It is the order of these bases that determines the inheritance of an organism. We call this sequence of bases the base sequence or DNA sequence. The sugar in DNA is always deoxyribose, an annular five-carbon compound (a pentose). The phrase deoxy shows that this sugar molecule lacks an oxygen atom present in ribose that is sugared in RNA. The phosphate is similar to that found in the ATP Nucleotides are linked together by strong covalent bonds (electron pair bonds) between the sugar molecules and the phosphates. In this way, the sugar molecules and phosphates form a backbone in the single thread, where the bases are free to bind to other molecules, e.g. they complement the bases on the opposite strand (see next page) or RNA (see page 148) on trans (uolsds.) To more easily describe the structure of DNA, researchers have agreed to number the five carbon atoms in the sugar contained in each nucleotide, from 1 to 5. The first carbon atom is called 1 '(read: one-labeled), the next carbon atom 2' (read two-labeled), etc. When nucleotides bind to each other to form DNA, this always occurs by a free hydroxyl group (OH group) of the 3 'atom of the sugar in one nucleotide forms a bond to the phosphate bound to the 5' atom of the sugar of another nucleotide. , so that the free OH group of the 3 'atom in the sugar of the leotide in the wire always binds to the phosphate of the new nucleotide. other 3 'ends as the figure next to it shows. New nucleotides can only be bound in The 3 'end of the thread. Researchers have agreed to write DNA from 5 'to 3' end, which is also the order in which new DNA single strands are made, ie replicated (copied).

Type 2 diabetes

Diabetes, is a disease that causes the blood to increase. There are two types of diabetes, type I and type 2. Type 2 diahe is also called lifestyle diabetes. This type increases especially after the age of 50, but today there are an increasing number of young people who develop such high-sugar D blood sugar levels at the same time as insulin is poor, and in part insulin production is reduced. The cells are resistant to insulin so do not absorb the sugar they need. If the disease is not bkr. Treated, it can lead to kidney failure, stroke and heart attack. Too much sugar in the blood can damage the smallest blood vessels in the body and cause down. set eyesight and amputation of bones and in men to impotence. For this type, a total of around 20 genes have now been found that can be linked to and disposed of for type 2 diabetes. Some affect insulin release in the pancreas, others the body's insulin deficiency, others regain weight gain and appetite. High incidence of the disease in certain families shows that hereditary factors are involved in deciding who is affected. If the lifestyle is healthy, the hereditary factors do not have to stand out. As many as 80-90% of aille with type 2 diabetes are obese. Too little physical activity is also decisive. Among people who are predisposed, the risk of the disease can be more than halved by reducing body weight when they are overweight using less saturated fat and more fiber in the diet and being in physical activity for at least 30 minutes per day. This lifestyle will also reduce blood sugar levels and keep the disease under control in sick people.

Genetically modified organisms in agriculture

Due to random mutations and gender reproduction, there is considerable variation between individuals within the same species. Through selection of individuals with desirable traits, humans have for a very long time bred plant varieties and animal breeds with many useful properties: greater yield, new colors, thinner fat layers, larger charcoal, better taste, etc. All our most common useful plants such as grains, potatoes , corn, rice, soy, apples, carrots and other vegetables and fruits are today the result of systematic processing. The same goes for the animals that give us meat and milk. But traditional processing by selection and crossing takes a long time and yields results that are difficult to predict because several properties are transferred simultaneously. With the help of genetic technology, it is now possible to select and modify or transmit one or a few genes and thus provide a desired trait relatively quickly. It is possible to transfer genes between species, eg F plants to animals. This could give properties that would otherwise not be bearable and that traditional processing would not have provided.

The diet and nutrient turnover

Earlier in this chapter, we have described glucose degradation both when it occurs aerobically and when it occurs anaerobically. Most of us do not eat any special foods with glucose except glucose-rich fruits. Other organic compounds in the food can also be involved in the degradation processes of the cell end by being transformed as the figure shows. Proteins in the diet are cleaved to amino acids. The amino acids are converted to pyruvic acid, succinic acid or fumaric acid, and they are further broken down by aerobic cell respiration. Food fats are broken down into fatty acids and glycerol. Glycerol is converted to pyruvic acid. The fatty acids are transported into the mitochondria, where they are converted to acetyl-coenzymeA, citric acid or succinic acid. This is how proteins and fats in the food give energy. If we eat more than we need to get building blocks and energy, both amino acids, glycerol, fatty acids and carbohydrates can be converted into fat. The fat is stored on the body, first as subcutaneous fat between the skin and the muscles, then between the muscle fibers. Food intake and energy consumption should be balanced so that we neither increase nor lose much weight.

Enzymes - building and behavior

Enzymes are essential for life on earth. Inside every living organ more a variety of chemical reactions occur. With the enzyme present, the reactions go up to several million times faster, the need for energy that gets the reaction started is reduced by up to s0. For each reaction one specific specialized enzyme is needed. more, and the enzymes needed to carry out these reactions are similar in all organisms both primitive and advanced, suggesting a common evolutionary origin. We often use the words primitive and advanced about organisms. By that we mean organisms that are simple or complicated built.

Fetal tests

Fetal diagnostics assume that cells from the fetus, taken from the amniotic fluid or placenta, are examined for chromosome defects or genetic diseases. It is possible to see if the fetus has too few or too many chromosomes, if parts of chromosomes have replaced space, or if there are specific genetic variations. Such studies are an offer to pregnant women who are at high risk of having children with genetic diseases or chromosome abnormalities. All pregnant women over the age of 38 at the estimated time of birth (term) are offered fetal diagnostics because of the increased likelihood of having children with chromosome defects. The sampling itself gives a risk of 0.5-1% for abortion. Prosthetic fertilization is most relevant to remedy infertility. However, in families with hereditary diseases, it may be appropriate to use this method because it allows the re-fertilization of fertilized eggs. In this way, it can be ensured that fertilized eggs inserted into the uterus do not contain the unwanted genes that allow the child to have the particular genetic disease. Such gene testing is called preimplantation diagnostics. In Norway, this method is only offered to those couples where there is a high probability that the brain will have a serious hereditary disease.

Dihybrid inheritance

For dihybrid inheritance, we look at the inheritance of two gene pairs placed on two different chromosome pairs. Mendel made crosses between pea plants that were different in two characteristics: seed shape (round or wrinkled peas) and seed color (yellow or green peas). In one experiment, plants that were homozygous for the dominant traits round / yellow peas were crossed with plants that were homozygous for the recessive traits wrinkled / green peas. The result was that all peas in the F1 generation became heterozygous round / yellow, as these are dominant features. When the Fl generation was crossed with itself, the result was four pheno types. round / yellow, round / green, wrinkled / yellow and wrinkled / green peas in the split ratio 9: 3: 3: 1. There is a typical cleavage relationship of dihybrid inheritance and crossing of heterozygous individuals with dominant decline. All sixteen possible combinations of dominant and recessive alleles for the two variants of the shape and color properties were equally likely. But because round shape and yellow color are dominant over wrinkled shape and Blind color, the split ratio between the four different phenotypes becomes 9: 3: 3: 1 (which together becomes 16, ie the number of possible combinations). This showed that the genes for seed color and seed shape were inherited independently of one another. Today we know that this is because the gene pairs for the shape and color properties lie on different (non-homologous) chromosomes. As we shall see later, the split ratio would have been completely different if the genes for the shape and color traits had been on the same chromosome. Another example of dihybrid heritage is eye color. Previously, eye color was used as an example of monohybrid heritage. We now know that the different variants of black, brown and blue eyes are due to two gene pairs on two different chromosome pairs. The genes work by giving the eye color different varieties of black, dark brown, light brown and blue depending on the number of dominant alleles. Whole black eyes are due only to dominant genes, AABB, while the brightest blue eye color comes from only recessive genes, AABB. In addition, we have other genes that affect the amount of pigment in epistasis (see page 187), where genes can be suppressed or augmented: to become colorless. Inheritance of eye color is thus much more complicated than we previously thought.

gene testing raises ethical issues

For genetic testing to be carried out by healthy persons, the etey nork law must be given genetic guidance. This is because one should be able to rely on the best possible information. Genetic guidance is provided by helper nell who is particularly qualified. The guide should provide information about the dmn disease to be tested for, the genetic test itself, what vome available from treatment options, and the risk that others in the family may inherit the same disease. Genetic counseling should also be provided after the results of the test are available. In the same way as for gentes Gentesting raises ethical questions, there is a need for guidance before one can be offered and pre-implantation diagnostics. The opportunities genetic testing provides, raise a number of ethical questions. For fellow Wnsouõeipso members in families with hereditary illnesses, a question arises: "Do I want to know or not to know?" Knowing if a genetic defect for the disease develops can be beneficial if the disease can be prevented or treated. But in many cases there is no effective treatment. The rules for gene testing of children under the age of 16 are strict, and it is only allowed to re-test children if the disease can be treated or is very important to get clarified whether the child will stay healthy or develop disease. Some examples of ethical issues: Should genetic testing be offered even in cases where doctors cannot offer treatment? - Can gene tests that show increased risk of developing serious disease. more, lead to poorer quality of life? - Should the family know the result of a gene test, or are you entitled to keep the result for yourself? Should insurance companies and employers be aware of the results of the gene test? Should people with hereditary genetic disorders in the family get a gene test when they want to have children? In connection with fetal and pre-implantation diagnostics, several difficult ethical questions also arise. Again, the tests will present teachers with the difficult choice: Should I choose to know or not to know what genetic diseases my future child is predisposed to? It is a question of whether the very offer of fetal diagnostics can be felt by the pressure of society towards the parents who apply, that they must not give birth to children with severe disabilities. Will future parents feel pressured into testing and possibly abortion? Are we heading for a sort-thin child who is not genetically normal, unwanted? For diseases for which there are good treatments against, e.g. PKU, it would be ethically questionable not to test the child. Although the increased knowledge of the human genome (see page 245) has given us the opportunity to develop gene tests for several diseases. Judge, there is every reason to believe that the research will eventually also provide new knowledge about how genetic diseases should be treated. However, it is important to be aware that we all, including those who are healthy, carry many gene defects that can lead to disease if the mutated allele is inherited from both parents. The standalone government-appointed body Biotechnology Login provides advice on the ethical use of biotechnology on humans and other organisms. You will find a lot of useful material on their website.

Chromosome mutations and disease

For several diseases and syndromes, the chromosome mutation is known. Fragile X syndrome is an example of a mutation in which a bit of the X chromosome is repeated over 200 times, as opposed to normally 10-50 times. If a daughter receives such a defective chromosome from her mother, it will have less consequences for her daughter if she has received an entire X chromosome from her father. If a son receives the mutated X chromosome from his mother, he develops the disease. From his father he gets a Y chromosome that does not contain the same genes. Fragile X syndrome delays development and impaired functioning, but the degree may vary. Chronic myelogenous leukemia, a form of blood cancer, is an example of a disease caused by a translocation on the chromosomes. Parts of chromosome 22 and chromosome 9 have replaced space, and a shortened, easily recognizable chromosome 22. A result is that a gene from chromosome 9 and one from chromosome 22 are spliced. The new gene encodes a protein that activates proteins that control the cell cycle. The rate of cell division of stem cells that are precursors to red blood cells, platelets of some white blood cells, is increasing. This is a change often associated with cancer.

The chromosomes are packed into the cell division

For the cell division, the chromosomes are packed so that they are short and thick. When a chromosome is copied and then packed, it looks like the letter X and consists of two identical DNA molecules that we call sister chromatids. The chromatids are attached together in the centromere. In all organisms, DNA binds to proteins that package it together. The packaging of heirloom is organized on several levels and is very precise. At the first level, the DNA double strand, which is 2 nm in diameter, is laced around proteins called histones. 10 nm strands are formed that look like beads on a string, each "bead" being called a nucleosome. The nucleosomes are packaged on to increasingly thicker threads, which are also coiled up to eventually form compact chromosomes. The composition of DNA and proteins is called chromatin. The chromosomes are made up of chromatin and shortened 10,000 times compared to the loosely packed threads after copying, and we can clearly see them in a light microscope. Each chromosome then consists of two identical tightly packed DNA molecules with a diameter of 700 nm. The total inheritance of an organism, ie the entire genetic information, is called a genome. In all organisms, there is at least one copy of the genome in each cell, distributed among a number of chromosomes that may vary from species to species. The human genome is divided into 46 chromosomes. Two chromosome sets, one from each of the parents, form 23 chromosome pairs. In total, each of the two chromosome sets has over 3 billion base pairs. If the DNA sequence were printed on paper, it would fill many hundreds of tightly written books. The total length of all DNA in a human body cell is approx. 2 m. The chromosomes then have the form of long thin strands. Before dividing a cell, all the DNA is copied so that each chromosome consists of two double strands. In the process where the mother cell divides these chromosomes into two daughter cells (cell division, either mitosis or meiosis), the chromosomes are packed as we described on the previous page, and the DNA is organized in an orderly fashion. We say that the chromosomes are condensed. The threads then become short and thick, allowing the cell to more easily handle the chromosomes.

Gender-linked inheritance

Gender-linked inheritance could just as well be called the sex chromosome inheritance. Of the 46 chromosomes humans have, two are sex chromosomes. The sex chromosomes in women (called XX) are homologous chromosome pairs, while men have two different sex chromosomes (XY). It is therefore only the man who can produce germ cells (sperm) with the Y chromosome, and who determines the sex of the offspring. The Y chromosome contains few genes, mainly male sex determinants. The X chromosome contains several genes, including genes that are not related to sex. Recessive traits bound to the X chromosome are therefore expressed in all males, but only in females that are homozygous for the recessive allele. Gender-linked inheritance was discovered when Morgan crossed a red-eyed wild-type banana fly with a mutant banana fly with white eyes. All the offspring in the F1 generation had red eyes. When males and females of the Fl generation were crossed with each other, the result was two phenotypes: banana flies with red eyes and flies with white eyes. All the white-eyed flies were males. Because all F1 progeny were red-eyed, Morgan concluded that the white-eyed allele was recessive. And since only males had white, Morgan concluded that the eye color gene was located on the X chromosome, with no equivalent on the Y chromosome. All genes on the X chromosome, recessive and dominant, will be expressed in males. In females, recessive alleles on the X chromosome are expressed only in homozygous individuals. Fathers can transmit genes on the X chromosome only to their daughters. Mothers can transmit genes on the X chromosome both to their daughters and to their sons. Genes on the sex chromosomes therefore have inheritance patterns that depend on gender. By sex-linked inheritance we write both alleles and letters for sex chromosomes. An eczema and heterozygous have X, X pel written. An example of a phenotype inherited by gender is redder color blindness. The property is due to a recessive allele on the X chromosome. The phenotype is expressed in all men who inherit the recessive cell, but in women only in those who are homozygous for the recessive allele. If we let F denote the allele for normal color vision and get the raisive allele, we get the following crossing scheme for a woman with a recessua allele and a man with normal color vision who have children together: We get three phenotypes: son with normal color vision, color blind son and daughters with normal color vision in a 1: 1: 2 ratio. Of the healthy daughters, one has the recessive allele and is the carrier of the trait. Since women must have the recessive allele in double dose, there are far fewer color-blind women than men. Another known example is blood disease, hemophilia. It is a chronic, hereditary and congenital disease caused by a defect in the blood supply mechanism. It can cause bleeding to stop, the trait is recessive, and the gene is on the X chromosome. The disease is therefore expressed in all boys who inherit the recessive allele. Girls need to have two mutated alleles to get sick, but it is very rare. Women who are heterozygous for the gene are healthy, but they can transmit the disease to their sons and the pathogenic allele to their daughters. From pedigree alone it is sometimes possible & find out if a trait is inherited as dominant or recessive, and whether the genes are on the sex chromosomes or autosomes.

Production of genetically modified organisms

Gene technology makes it possible to transfer genes between organisms belonging to different kingdoms. Because the genetic code is universal, a gene will code for the same protein in a bacterium as in a human. Often we also see that foreign genes confer similar properties in a new organism that ae did in the organism from which they were derived. This makes it possible to produce organisms with new desired properties. Production of a genetically modified organism is a process that takes place in many steps in a particular order. At each stage, researchers use DNA techniques that have specific purposes. You could read more about some of them in the table in the previous section. The starting point for the production of genetically modified organisms is that we know the DNA sequence of a particular gene that gives a desired trait. Such a gene can be cut from purified DNA. It is also possible to create cDNA from mRNA and thus select a gene that is expressed in a particular cell type. To transfer the selected gene from one organism to another, a vector is needed. A vector is a DNA molecule in which foreign DNA can be inserted. Because many copies of the vector are made in bacterial cells, the foreign DNA is also copied. The vector is then used to transfer the desired DNA to a new organism. To increase the possibility of a successful gene transfer, it is necessary to have many enough copies of the DNA to be transferred. The most commonly used vectors are bacterial plasmids. This is because they are practical and easy to work with. It is easy to clone DNA pieces into plasmids. Plasmids with different properties for different purposes can be purchased. It is easy to insert foreign DNA into plasmids that can then be traced back to bacterial cells. Bacteria quickly divide and make many copies of the plasmid vector with foreign DNA. This is called DNA cloning and is usually the starting point for the transfer of genes between organisms. Virus is another type of vector. It is possible to replace parts of the genetic material of different viruses with foreign DNA that we wish to transfer to other organisms. Both adenoviruses, which cause colds, and retroviruses, the transmission of genes to humans. Viruses used as vectors are genetically modified so that they are unable to multiply and develop disease. which can be a cause of cancer, among other things, used as a vector by.

Gene therapy

Gene therapy means first and foremost the use of genetic material to treat disease. Simply put, it is adding new genes that can replace or repair genes with errors. The inserted gene can cure disease by producing proteins that the body needs, but which the patient cannot make even due to gene defects. A prerequisite for this type of gene therapy is that the gene defects that cause disease are known, and easiest will be there. as the disease is due to a mutated gene, ie it is a monogenic disease. Gene therapy is also used in the treatment of non-monogenic cancers. Then it is not healthy genes that are attracted, but suicidal genes that make proteins that kill the cancer cells, or genes that improve the patient's immune system. This seems to be a simpler procedure than curing sick cells. Gene therapy can be used to treat body cells in specific organs that do not function properly. The cells can be in the patient's body. Men may be more effective in removing cells from the patient, culturing them artificially (1 culture) outside the body, supplying the right gene and eventually returning the cells to the patient. Already in the 1990s, gene therapy was used on children with immune deficiency disease X-SCID. Normally, this disease will lead to it already at the age of 2, but with the help of gene therapy several children were healed In the early 1990s, there were high expectations associated with the gene pi. It was envisaged that now it would be possible to cure a number of diseases In recent years, several successful trials have been made to cure sick judgments, and gene therapy has now been approved as a way to treat certain diseases, including Folling's disease (PKU , see page 207). However, the use of gene therapy today is not routine when it comes to treating patients, and the technology is still at the experimental stage. There are major technical problems associated with the methods themselves. Normally, the transferred DNA will be integrated at random sites in the patient's chromosomes. This can be unfortunate and, among other things, few are inactive, ie no effective proteins are formed in the right amounts. Other important genes may be disrupted. That children treated with gene therapy for a disease, later unexpectedly developed blood cancer, suggests. about the result that they supplied the genes The most widely used method of transmission was to use different viruses as vectors (see page 233). But our immune system responds to viruses, so the method can only be used once per patient. In addition, it is somewhat uncertain how safe it is for patients to use viruses. Gene therapy is today an immature technology, and that of human genes Much research is being done to meet the technical challenges and develop less risky methods, among other things in order to achieve a more efficient and safe gene transfer. In the Biotechnology Act, gene therapy is defined as the transfer of genetic material to human cells for medical purposes or to affect biological functions. This definition is very broad and will also include gene transfer used to improve properties, e.g. performance in the context of sports, then it is called repopulation.

Gene therapy and ethical issues

Gene therapy on body cells also raises ethical issues. Should the method be equated with other medical treatment? A major problem is that the method is very resource intensive. Can it be justified to spend large resources on uncertain treatment of rare diseases when many patients suffering from other and more common diseases can be treated at the same cost as one gene therapy treatment costs? As the technology can be used to cure diseases, it can also be used to improve features such as appearance, performance and intelligence. What characteristics should be allowed to change in gene therapy? If gene therapy is used on germ cells or on fertilized egg cells, the gene change will be inherited to future generations. This can be an effective way to eradicate future serious genetic diseases for everyone from families who have suffered from such disease for generations. However, it raises questions about human dignity. It is also ethically questionable to "improve" future generations because the consequences are so great and unclear. The gene transfer could have negative consequences that first appear in later generations, and they have not had the opportunity to make this choice themselves. Gene therapy used on germ cells or to improve normal characteristics is prohibited in Norway today. Such therapy should only be used to treat serious illness or to prevent such illness from occurring.

Antibiotic resistance

Genes for antibiotic resistance are often used in plants as well as in bacteria as a check that other genes are transmitted, so-called marker genes (see page 234). It has now been shown that bacteria in the intestine of humans can absorb the antibiotic resistance genes found in genetically modified foods. If the disease-causing bacteria become resistant, this can mean that important antibiori cannot be used to fight them. Although bacterial uptake of genes from food into the gut is a rare occurrence, the consequences are large enough for the EU to adopt a directive requiring exposed GMC plants not to contain genes for antibiotic resistance. In parallel with this, nine other marker genes are developed with lower potential risk to the environment and health. If both genetically modified and non-genetically modified plants are grown in the same area, clear rules and good routines are important to avoid mixing these plants. This can be done by having large buffer zones. This reduces the likelihood of pollen spreading by wind or animals. Care must also be taken to ensure that genetically modified seeds are well marked and that farmers are sure to understand what it means to grow genetically modified plants. Those who transport and receive the products from genetically modified plants must also have systems for handling both genetically modified and non-genetically modified products without mixing them. The proportion of genetically modified plants grown in the world is growing. In many places, there are not sufficiently good systems to prevent mixing of genetically modified and non-genetically modified seeds, which has made it difficult today to guarantee that, for example, a corn box is completely free of genetically modified maize. No genetically modified maize varieties have been approved in Norway for the time being. If there is more than 0.9% of a genetically modified ingredient in a food, the food must be labeled "genetically modified".

Investigation of CDNA libraries

If we want to study the inheritance that gives a cell specific properties, it is often the genes we will look at. 95% of our genetic material contains no genes. Additionally, it makes sense to study the part of the genes encoding mRNA, which we can do by isolating mRNA from the cell type we want to study. Then we make a single stranded DNA copy of each mRNA by which the genes are usually split up by non-coding sequences. using an enzyme (reverse transcriptase) that can use mRNA as a template. This is called complementary DNA, or cDNA (c is the abbreviation for the English word complementary). (In the next section you can read more about this process.) This next provides double-strand DNA, which can be pasted into a plasmid and transferred to bacteria. This is a form of cloning (see page 255). Each plasmid with inserted cDNA we call a clone, and a collection of clones based on the same cell sample is called a cDNA library. Such cDNA libraries can then be used to find genes that are expressed in the cell type the mRNA was isolated from. Cancer cells can be used to find disease-causing mites that are important for the development of cancer. As you read on page 151, mRNA can be nurtured on an alternate feeder Then the same gene wiwa l there different protelens All the different splicing variants of mRNA expressed in the cell type will be copied as cDNA, if you add the DNA in cell, you will not bring with you this information about how genes becomes expressed.

The structure of the DNA

In 1953, biophysicist James D. Watson and biochemist Francs Crick published an article describing the structure of the DNA molecule. You can read this article on the Bios website, the article was just one page with 122 lines, yet it has been characterized as the greatest scientific achievement in biology, and the two researchers were awarded the Nobel Prize in Medicine in 1962. The discovery of the inheritance structure became the introduction to what we like to call the biological revolution and has provided the basis for much of the new knowledge we have today in biology and medicine.

Sequencing of DNA

In DNA sequencing we find the order of bases in a DNA molecule. Then you can identify which gene you are working on, and that is a prerequisite for many other studies and analyzes, e.g. cloning of genes, species determination or detection of genetic diseases. Today, the entire genome, the genome, has been completely sequenced in many species. The amount of information about DNA sequences is so enormous that we need to have powerful computers to store and analyze it. A widely used sequencing method is to add enzymes that first cut the double strand into pieces, and then make single strand DNA. Then ordinary nucleotides are mixed with nucleotides which in structure are slightly different nucleotides in DNA. The altered nucleotides that are added lack an OH group and are called dideoxynucleotides (abbreviated dd). This new DNA strand with dideoxynucleotides is formed piecewise from the same starting point, because the missing OH group means that the DNA strand cannot be extended further. The DNA pieces can be separated by size of a gel and then read off, sequenced. Today, this sequencing takes place automatically using machines.

Norwegian legislation

In Norway, the Biotechnology Act (Act on Human Medical Biotechnology) and the Gene Technology Act (Act on the Production and Use of Genetically Modified Organisms) regulate research and use of biotechnological methods. It is allowed to research fertilized eggs, aborted fetuses and human births. An important condition, however, is that those who give the material know what it means to give the material to research, and that they have given a clear consent that it can be done. All research involving people must also be recommended by a research ethics committee. Such a committee will, among other things, assess whether the research is ethically sound. The cloning of Dolly meant that people's cloning could also be possible in the near future. That individuals, fanatical sectarians or elite soldiers were to be cloned - often in large numbers - was easy to imagine, and this spread fear. Many countries, including Norway, soon enacted a ban on human cloning. Therapeutic and reproductive cloning is prohibited in Norway. Research on fertilized eggs and isolation of embryo stem cells was prohibited in Norway until 2008. It is now law, and we now have legislation that is in line with many other countries.

Metabolism

In a car engine, gasoline and oxygen are converted into carbon dioxide and water through a series of chemical reactions. At the same time it is released eneroi Some of the energy is released as heat, the rest helps the car move see We can compare your body with this car. Food and oxygen are converted to carbon dioxide, water and energy just as in the automotive engine. In decomposition processes, energy is released as the molecules of enzymes react and form new and smaller compounds. Small molecules can be transported with the blood around the body. There they can be building blocks so that the body can assemble small molecules into large molecules, or they can be broken down further and release energy that can be utilized to, for example, transport molecules and ions through membranes called active transport, or to give the organism body heat. The sum of all the processes in which energy and building blocks are bound or released, we call metabolism, metabolism. Metabolism consists of two main parts: anabolism and catabolism. The structure of small molecules into large molecules is called anabolism, while the breakdown of large molecules into small molecules is called catabolism. Each of the sub-reactions in metabolism is catalyzed by a specific enzyme. In catabolism, large organic molecules can be partially broken down and used for building blocks in new compounds, or they are broken down further into cellular respiration. Cell respiration may be aerobic, ie with oxygen, or anaerobic, without oxygen. Some organisms have only aerobic cell respiration, others do not need oxygen and thus have anaerobic cell respiration, while some organisms may alternate between aerobic and anaerobic cell alteration depending on the oxygen content of the environment.

Aerobic cell respiration

In aerobic cell respiration, oxygen is required. Many animals have gas exchange organs and a circulation system that ensures that oxygen can be transported into and around the body, and that some of the waste after cell respiration - the carbon dioxide is carried out. Plants also have aerobic cell respiration, and in plants, air diffuses with oxygen gas and carbon dioxide gas out and in through the gap openings in the leaves (see page 81). Sheep cells and plants can absorb enough oxygen and get rid of carbon dioxide by diffusing directly through the cell membrane of each cell. Here we will take a closer look at the breakdown of glucose. Later in the chapter we will look at how other organic molecules from our food - proteins, fats and large carbohydrates - break down. Aerobic degradation of glucose consists of many partial reactions. We group them into three main sections: • Glycolysis Cancer cycle • Oxidative phosphorylation In the first two main molecules, molecules are cleaved several times, releasing energy that is transferred to energy carriers in the form of ATP, NADH and FADH. In the third part, energy from NADH and FADH, which was formed in the first two main parts, is used to generate ATP. We consider ATP to be the most useful form of short-term stored energy.

Bacterial gene regulation

In bacteria, control of enzymes involved in metabolism can take place on two levels: First, a bacterial cell can regulate the activity of enzymes found in the cell, e.g. by allowing the first enzyme in the reaction pathway of a product to be inhibited by the final product (see page 58). This mechanism is rapid and enables bacterial cells to adapt rapidly to changes, e.g. changes in the nutritional approach. Second, the bacterial cell can regulate how much it should make from certain enzymes. In bacteria, genes with similar functions are organized one after another in saccade operons. A long mRNA is formed which encodes several proteins, e.g. enzymes that are part of a series of chemical reactions. When the bacterial cell has no use for the enzymes, the transcription of the entire operon can be stopped. This saves the bacteria from unnecessary energy and resource use. When there are nutrients that the bacterium needs, an operon can be activated so that the cell produces the enzymes it needs. End products made by the bacterium itself can stop transcription from the operon. This is called self-regulation and means that certain molecules can turn on or off the transcript. In an operon, several genes with similar functions are sequenced and are transcribed as a coherent mRNA. An example of a self-regulated operon is the lactose operon in E. coli. This operon encodes the enzyme necessary for cleavage of lactose to glucose and galactose. But this operon is only transcribed when lactose is present and glucose is not present. This is due to a complicated interaction between E.coli's own proteins and the carbohydrates lactose and glucose. mRNA is broken down more rapidly into prokaryotic cells, e.g. bacteria, than in eukaryotic cells. It allows bacteria to stop production of some proteins faster and to start production of others. Furthermore, the transcription from DNA to RNA is not controlled to the same extent by transcription factors.

How these energy carriers work

In cellular respiration, NADH is formed by NAD + absorbing one H * ion and two electrons through a series of energy-consuming reactions, and in a subsequent reaction NADH is cleaved again. In the cell respiration, FADH is also formed through reactions where energy is supplied and FAD takes up two H ions and two electrons, and then it is cleaved. The energy supplied in the reactions that form NADH and FADH comes from the breakdown of nutrients, and this energy is then used to form ATP. In photosynthesis, NADPH is formed when the chloroplasts absorb solar energy. NADP takes up one H * ion, two electrons and energy, and in a subsequent reaction, NADPH is cleaved again. The energy from this reaction is used to produce glucose. You can read more about this in the next chapter. The figures below show simplified models of NADH, NADPH and FADH, and how they emit hydrogen ions and electrons. Hydrogens and electrons are transferred to other molecules, and we get chemical reactions that emit energy.

ATP as a cofactor

In metabolism it is ATP's ability as an energy carrier we emphasize. ATP is also a cofactor of a group of enzymes, the phosphorylases. Phosphorylases are found in all cells. Phosphorylase has an active site where there is room for substrates, and in order for the active site to have a shape suitable for the substrate, the phosphorylase must have the coenzyme ATP attached to it. The phosphorylases participate when small molecules are to be assembled into large molecules, e.g. when the monosaccharide glucose is to be built into the polysaccharide glycogen, or when large molecules need to be broken down into smaller ones, e.g. glycogen for glucose. The reaction that takes place during the build-up of glycogen requires energy, and this energy is supplied in reactions where ATP is included and is cleaved to ADP and P. On the contrary, the decomposition of glycogen into glucose occurs, the energy that is released can be used, among other things, to: ADP and P again form ATP. For each glucose molecule that is attached to another, energy is needed from three ATPs. When glycogen is cleaved into glucose molecules, two ATPs are released for each glucose molecule that is cleaved off from the glycogen molecule. The figure next to it shows how the glucose molecules are built together. The phosphorylase has an active seat with space for three glucose molecules. With the help of energy from ATP, bonds are formed between the glucose molecules, so that we get a carbohydrate of three glucose molecules that are attached together. Subsequently, two other enzymes participate in two sub-reactions that bind several of the glucose chains to a large glycogen molecule.

Genetically modified organisms and the environment

In the Norwegian Gene Technology Act, social benefit, sustainability and ethics are independent assessment criteria in addition to the consequences for health and the environment. Genetically modified organisms are not in use in Norwegian agriculture today (2013). Several other countries also have a restrictive policy regarding the use of such organisms outside the laboratory. The reason is that we have little knowledge of possible negative consequences for health and the environment. Few studies have been done on the long-term consequences of GMO use, but GMOs represent a potentially serious risk to traditional agriculture and to ecosystems. When it comes to the environment, there are two types of negative consequences that are feared. First, scientists are afraid that genetically modified organisms will have growth benefits and be able to invade natural habitats. In nature, GMOs will be able to change the natural ecosystems by outperforming other species. Second, it is feared that genes will spread from the GMO species to wild species, both by gender and non-gender transmission, often between different organism groups. The wild species may have the same beneficial properties as the genetically engineered ones, and this can be negative in an ecosystem. The risk of negative effects will in each case depend on several factors: What properties are transferred to the modified body organism? The greatest risk to the environment is if the new properties provide benefits in competition with wild species or if they are detrimental to the environment. - Can the genetically modified organism establish itself and survive in the wild? For some agricultural plants, the Norwegian winter will be too cold for the species to survive in Norwegian nature and establish wild populations, even with some newly added genes. Are there wild populations or close relatives that the genetically modified organism can cross? Doing so increases the likelihood that the new genes can be transferred from the genetically modified organism to wild relatives who may acquire new traits with negative consequences for the environment. For example, a plant such as maize does not have wild relatives in Norway. Nor will it survive Norwegian winter. Nor do the domestic animals have close relatives in Norwegian nature. GMO sheep are therefore not likely to have any environmental effects other than unmodified sheep. Grass, grain and rapeseed, on the other hand, have wild relatives in Norwegian ecosystems. Therefore, there will be an increased risk of transmission of genes from genetically modified species of grass, grain and rapeseed. From GMO plants, genes will be spread through pollen to related species in the wild. In particular, wind-pollinated species will be able to spread pollen far, up to 21 km has been detected for grass species.

The evolution of genetics

In the middle of the 1800, monk Gregor Mendel crossed pea plums fre Ase how certain traits were transferred to the next generation. In well-planned trials, he undermined a trait at a time. He selected seven characteristics that were clearly defined, for example, plants that either produced yellow or green peas, or that had purple or white flowers After crossing the plants, he talked about how many of the offspring had pitted their parents' characteristics. free first generation to assert itself, which was decisive in advance how the properties were inherited. In doing so, he was able to formulate testable property transfer laws. Although Mendel did not know what the genetic material or genes were, he discovered important properties of the genes. Recent knowledge of how the chromosomes divide the meiosis has confirmed Mendel's promises. Mendel published his results in 1866. They received little notice of his time, but were rediscovered and recognized in 1900. Mendeli's method of genetic analysis, that is, counting offspring with specific traits after crossing experiments, was up to the evolution of molecular genetics 1950s the only method we had for studying inheritance Around 1910, the banana fly took over as a precursor organism in studies of American American Thomas Hunt Morgan found evidence that inheritance traits was located on chromosomes. He discovered sex-linked inheritance and used cross-linking between linked genes to map the genes' location on the chromosomes. You can read more about this later in this chapter. The genus was identified as DNA by Oswald Avery in 1944. The three-dimensional structure of the DNA double strand was first discovered by Rosalind Franklin and then explored and published by James Watson and Francis Crick in 1953. In 2001, a draft with most of the the base sequence in human DNA was published, and the entire sequencing project was completed in 2003. Common to diploid organisms is that the nucleus contains two sets of chromos. summer, one set inherited from each parent. The 22 pairs of autosomes constitute 22 homologous chromosome pairs in humans. The chromosomes in a homologous chromosome pair have the same size and contain genes for the same traits. Thus, genes for the same traits come in called pairs and gene pairs. The gene pairs are located in exactly the same position on the two chromosomes. The position of a particular gene on a chromosome is called a locus (of the Latin locus = locus). A gene is often found in several variants. It gives variation in the same property, e.g. free or firm earlobe. Such different versions of the same gene are called allele genes or only alleles.

DNA regulates the amount of enzymes

Inside each cell, thousands of different enzymes are produced. Some enzymes are produced in all of our cells, while other enzymes are produced in just a few cell types or tissue types. Examples of enzymes that must be produced in all cells are the enzymes that participate in the copying of DNA and in the cell division itself. Also repair enzymes as at any time can repair small damage, small mutations in DNA, must be found in all cells. In a cell, the DNA controls which enzymes are formed and the amount of each enzyme. The cell operates such an assay control by the fact that the DNA controls the protein production, ie also the enzyme production.

Are clones completely alike?

It's not just the genes that control how we develop; environmental impacts also have a lot to say. Here, among other things, epigenetic mechanisms come into play. That is what we came up with in Chapter 5. Therefore, two clones will not necessarily look the same even though they have the same inheritance. In fact, two clones are likely to be more different than single twins. When single twins grow up together, in addition to having the same inheritance, they will often receive relatively similar environmental impacts. However, clones will often be born at different times and receive different environmental impacts. An example of clones being different is the coat color of some animals. For example, the fur color and drawings of cats are controlled by genes located on the X chromosome. Female cats have two X chromosomes, but are only active, will vary, and the coat color and drawings may therefore be different from the original and one X chromosome is activated, which of the two X chromosomes is the clone.

ATP - an energy carrier

Many chemical reactions occur all the time in the body. Some of this energy doesn't get started by itself. It must be linked to the gut with one of these reactions. It happens by transferring energy from one reaction that requires energy, the other gives off energy. One reaction that requires is molecules that can couple a reaction that can release energy. Energy carriers c In all chemical compounds, energy is stored in the form of chemical. When chemical reactions take place, the substances that react can have atoms removed or get atoms or functional groups from an energy carrier. In this way, the new substances that are formed become more energy-rich. Only then can they be included in further reactions and the energy can be released. Energy carriers can then store this energy and use it to drive other reactions that require energy, including in the build-up of large compounds such as fat and polysaccharides D to find an overview of these and other large compounds on the Bios website substance to another. Energy. 80 Energy-bearing or energy-carrying molecules are involved in reactions that are transferred to another molecule. In living organisms we find several different energy carriers for energy. The most important is ATP, adenosine triphosphate, a molecule with three phosphate groups. The bonds between them are unstable. In energy-demanding reactions in the body, ATP can transfer one phosphate group to another molecule, thus increasing its chemical energy. Then the molecule can participate in reactions that would otherwise not have been possible. In some energy-bearing molecules in living organisms, the ability to bind and transfer energy may be linked to hydrogen atoms in the form of electrons (e) and hydrogen ions (H) which are bound to the molecule. These electrons and ions then make the molecule more energy rich. In some textbooks you can see that the word electron carrier or hydrogen carrier is used about these molecules instead of the word energy carrier. Examples of such energy-carrying molecules are NADH, nicotine amidadenine dinucleotide, NADPH, nicotinamide adenine dinucleotide phosphate, and FADH, flavin adenine dinucleotide. You can read more about these energy carriers in section 2.6. Both ATP, NADH. NADPH and FADH, we call short-term energy storage or fast-energy storage. They are constantly involved in chemical reactions as the organism needs readily available energy.

Mutations + Lifestyle = Health

Many known diseases are due to defective alleles due to point mutations. With the exception of a few necessary bases, most of the gene is still intact. However, the protein it encodes does not work properly. In some cases, the defective allele is recessive and must appear in homozygous form for the disease to occur. In other cases, the defective allele is dominant and leads to disease in heterozygous form. however, the environment will have a great impact on whether the disease develops. Then it can play a big role if you are hereditary predisposed to the disease. Inherited or "predisposed" means that a person has genetic variants that are more likely to have a given disease than a randomly selected individual in the population. It is the interaction between environment (eg lifestyle) and genetics that determines whether the disease breaks out. An example of the environment may be sex hormones that cause some diseases to start to appear in adulthood. In many cases, the lifestyle can determine if the disease spreads. The lifestyle has to do with environmental factors such as diet, physical activity, smoking and alcohol consumption.

DNA bits on chips - micrometry technology

Micrometry technology is a new technology that has enabled us to analyze many genes at once. With the help of robots, it is now possible to attach small pieces of single-stranded DNA from all known human genes on forged gene tags. Such chips are called micromatrices. Simply put, we can say that a tag = an individual's genome, and that a route = a gene. The chips are divided into a grid so that individual threads of each gene are now placed in the known position. If we create single-stranded cDNA from mRNA expressed in one particular cell type (see the figure on the previous page) and spread it over the tag with genes in known position, the cdNA from the cell we want to investigate will bind to DNA on the tag. The DNA from the cell we want to examine is labeled with a dye (fluorescence), and we can easily see which genes on the chip have DNA from the cell attached to it. It provides information on which genes are expressed in the cell type and which are not expressed. For example, this method can be used to compare gene expression between two different cell types, or between normal cells and cancer cells from the same organ. This makes it possible to find out which genes are more or less expressed in cancer cells compared to normal cells. The cDNA contains only the active genes in a cell type. The gene tag contains all the genes from an organism distributed in its own route, so CDNA will only attach itself to some of the routes on the gene tag. The gene tag can then be illuminated, and only those squares that have cDNA attached to it will fluoresce. Thus, the gene tag shows what kind of genes are active in the cell we are analyzing. For example, we can use the method to investigate which genes are active in lung cancer cells and which genes are active in normal lung cells. Knowledge of such genes can be important when it comes to making the right diagnosis, ie not only deciding whether it is cancer, but which type of cancer it is. This can be important in order to detect the cancer early and give the individual patient proper treatment. The method is also used to detect if any genes are found in fewer or more copies of the genome than normal, which is often found in cancer cells.

Important DNA Techniques

Modern biotechnology uses a variety of techniques. Some of them are thousands of years old, such as making crosses and selecting individuals with desired characteristics, and using microorganisms in culture. But what we now call genetic technology, we started in the 1970s, following the discoveries in the 1960s of restriction enzymes that cut the DNA strand at specific sequences, and ligases that could glue DNA strands together. Until then, DNA had been the most difficult molecule in the cell to analyze because it is so far. The restriction enzymes and ligase made it possible to clone smaller pieces of the DNA strand, and then the DNA could be analyzed. In the latter half of the 1970s, sequencing methods were developed that made it possible to read the sequence of bases in DNA, what we call the DNA sequence or genome. When the polymerase chain reaction (PCR) was developed in 1985, there was a revolution in this field. The technique makes it possible to make a huge number of copies of the DNA bits you want. This simplifies many of the basic techniques, and thus the human genome was completely sequenced in 2003. After the DNA sequence in the human genome (and eventually the genome of many other organisms) became known, it has become possible to perform Renom assays where all the genes in a cell or in a tissue type are studied simultaneously on DNA, mRNA or protein -level. The most important tools for studying differences in gene expression (eg between cancer cells and normal cells) are micromatrices and bioinformatics. They make it possible As the DNA sequence of most of human genes is now known, it is more interesting to study the functions of the individual proteins and how they interact with other proteins in the cell. In order to find genetic variants that can cause disease, new genetic tests are constantly being developed. For more and more of the genetically related diseases, treatments can be developed that are specially tailored to the mutations in each patient, e.g. in connection with cancer. judge. Whether you are investigating the function of a gene, performing a gene test, producing large amounts of a particular protein, sequencing a genome, or making a gene-modified organism, there are some DNA techniques that underlie it. We will look at some of the most important of these to process large amounts of information in an effective way.

Monohybrid inheritance

Monohybrid inheritance of seed form in pea plants, ie whether the peas became round or wrinkled, by crossing homozygous plants that yielded round peas, with homozygous plants that gave wrinkled peas. Monohybrid heritage is when we look at the inheritance of only one gene pair. The parent generation is called the P generation. The next two generations are F1 and F2. Because parental generation was allele for allele, each parent formed germ cells of only one genotype Plants giving round peas, had germ cells with the allele R. Plants giving wrinkled peas had germ cells with genotype r. combining the F1 genera ion. All offspring had the genotype Rr and gave round peas. Of that homozygous and two t, Mendel could conclude that the round seed shape allele is masks, hides, the wrinkle seed allele. dominant, and that Mendel let Fl plants pollinate themselves. Because these plants were heterozygous and had two different seed alleles, they produced two types of germ cells in equal quantities: R and r. Therefore, there were four ways the F generation alleles could be combined in the F2 generation. The F2 generation yielded three different genotypes: RR (4), Rr (24) and rr (4). Since Rer is dominant, 4 of the phenotypes will be round. The ratio between the round peas of the phenotvn and wrinkled peas is therefore 3: 1. We say that the split ratio e. 3: 1. Only when we have a large number of offspring should we expect that 4, or 75%, of the peas will be round. When we have individuals with a dominant phenotype, it is impossible to know if the genotype is homozygous or heterozygous (RR or Rr in the pea example). However, it is possible to determine the genotype by crossing an individual of unknown genotype with an individual that is homozygous recessive The relationship between phenotypes among the progeny will then reveal the unknown genotype. This type of crossing is called test crossing (see figure overlook next page). The test crossing method was developed by Mendel. It is still used, especially in animal and plant breeding, where it is important to know the genotype. In humans, test ethics cannot be tested purely ethically to test the genotype. Alternatively, geneticists have analyzed the results of crossbreed that has happened, and made pedigrees based on phenotypes of people who are related. Pedigrees based on phenotypes show inheritance of one or more traits. Now let's go back to the example of tongue rolling. The ability to roll the tongue together into a longitudinal tube is genetically determined, and the "roll" pheno type is a dominant trait. Because we know that "non-rollers" are homozygous for the recessive allele, we will often be able to reason for the genotype of this trait for some individuals in a pedigree. Similarly, pedigrees can be used to arrive at the genotype for a number of other traits, based on phenotype. For several genetic diseases, the difference in the base order of healthy and pathogenic alleles is known. Then healthy individuals with pathogenic alleles (such individuals are called carriers) can be revealed by genetic engineering methods, so-called gene tests (see page 205). The fact that a person is a carrier means that she or he has the allele that gives rise to the disease without any effect or effect. The allele can be passed on to offspring that can develop the disease.

Most enzymes are proteins

Most enzymes are proteins. Proteins are made up of rows of amino acids bound together with so-called peptide bonds. We call such rows polypeptides. Polypeptides are folded crosswise using bonds between the atoms. In this way, the polypeptides have a three-dimensional structure. When the polypeptides have obtained this structure, we call them proteins. The three-dimensional structure is essential for the function of the protein. You can read more about the various amino acids on page 153. The enzymes are important proteins in living organisms. A few enzymes consist only of proteins, but most enzymes also have an additional factor, a cofactor, linked to the protein, Some cofactors are metal ions. Other cofactors are organic molecules. We call them coenzymes. The cofactors participate when the polypeptide is folded into a three-dimensional protein, and the three-dimensional shape determines which substance can be stuck to the enzyme. The figure next shows how cofactors hold the long polypeptide chain together in several places, and how the enzyme has a three-dimensional shape with space for the substances to react, the substrates. An enzyme consists of rows of amino acids bound together with peptide bonds to give us polypeptide chains. The figure shows how amino acids are bound together by peptide bonds (colored red). The polypeptide chain is coiled and has a three-dimensional structure. It has one or more cofactors. R is a variable group which gives different properties to the different amino acids.

Stem cells in research and patient care

Much of today's basic medical research aims to find out how the body's single cells and the DNA in the cells work. In this work, the stem cells are central. Studies of stem cells make it eczema. It is possible to find out how cells are regulated, what controls which cell types to produce, and how cells "talk" to each other in the body. If the researchers in detail understand how stem cells work and are regulated, that knowledge can in principle be used to create any type of cell. It is conceivable that it will be possible to produce specialized cells that can be inserted into patients. An example: A patient with a damaged heart may have new heart muscle cells transplanted from the patient's own stem cells. The same can be done with insulin-producing cells, nerve cells, skin cells - yes, in theory, all kinds of cells that the human body needs to function. In the future, we may also be able to make tissues or parts of organs, not just cells. Many believe that this will open up an opportunity to treat diseases for which we do not currently have adequate treatment methods. When we know how the growth of healthy cells and their DNA is regulated, it becomes easier to understand what happens to disease. For example, cancer and allergies are caused by some control mechanisms not working properly. If we know what is the cause of a disease, it may be possible to develop new treatment for it. Several sites around the world are advertising clinics on their websites that they can cure patients with incurable disease using stem cells. These clinics take a good look at the treatments. At present, these treatments have not been documented. Rather, on the contrary - serious side effects have been reported. Stem cell scientists around the world walk away from this activity, which is also referred to as stem cell tourism. Researchers believe it is wrong to offer such treatment to sick people.

Examples of epigenetic effects

Much research has been done on how fetuses can be influenced through o genetic mechanisms. A study showed that mice born with food with a high alcohol consumption during pregnancy are at higher risk of 8 offspring with fetal alcohol syndrome (FAS). The study suggests that the mental and physical defects that characterize these individuals may be partly due to epigenetic mechanisms. A few years ago, a study from Sweden showed that there was a correlation between the rate of diabetes in children and how their grandfathers and grandmothers starved when their grandparents were in puberty and in their mother's life in the 1930s, respectively. A number of later studies shows that environmental influences such as stress, diet and temperature in one generation can affect the next generation without changing the genes themselves. What is interesting is that these inherited changes in the phenotype do not reflect changes or mutations in the DNA sequence of the genes themselves, but among other changes in the histones and thus in the way the DNA is packaged. It has also been shown that male rats that were exposed to a fungal poison at the fetal stage had an increased risk of developing cancer and renal failure. These effects were transmitted for three successive generations, and it turned out that there could be a change in methylation (see page 162) of the DNA in the sperm. This shows that epigenetic mechanisms are transmitted not only from cell to cell through normal cell division (mitosis), but also through the type of cell division that produces germ cells (meiosis). Thus, epigenetic changes, with their effects on gene expression, can be transmitted to new generations. later generations. Probably they will gradually decline.

Mutations

Mutations can cause diseases Permanent alterations of the bay sequence in DNA are termed as having readymade DNA corrected in advance of the cleavage, causing multiple repair enzymes to cure and repair damage to the DN threads. Still, there are still errors that are not corrected pp. While body cell actions only have consequences for the individual being selected, mutations that occur in the sex cells can be transmitted until new gene zones are like new alleles. Although most mutations are not negative, viwa cases can have serious negative consequences. If the mole zone is without a gene, it probably will have no consequence. Since approx. 95% of our DNA contains no genes, most of the mutations present will have no effect. If the mutation occurs within a gene, it can get negative rims by giving incorrect instruction and deming the wrong stroke. trip on the protein, Some mutations can have a beneficial effect and a decisive effect in evolution. However, most mutations are neutral. Some are negative, and a few are fatal and fatal (lethal) Broadly speaking, we can divide mutations into two types: point mutations and chromosome mutations.

How these energy carriers are built

NADH and NADPH are quite similarly built. They are both made up of ribose, adein and two phosphate groups, ie ADP, and both contain a molecule B, vitamin (niacin). The difference between NADH and NADPH is that NADPH has extra phosphate groups that NADH does not have. That's what the letter P at the end of the naynet shows. The NADPH amphibian group is attached to the ribose. We need the supply of B vitamins through the food we eat. Only small amounts are needed, and B vitamins are therefore considered as micronutrients. Of such micronutrients, we usually need between 2 µg and 2 mg every day. We need such small amounts because NADH and NADPH are reused. NADH and NADPH are cofactors in several dehydrogenase enzymes found in the mitochondria and chloroplasts. Without the cofactors, the dehydrogenases do not work. Dehydrogenase enzymes have this name because they help when hydrogen ions - and possibly electrons - attach to or release from molecules. FADH, is also made up of ribose, adenine and two phosphate groups, ie ADP. In addition, FADH, a molecule B, contains vitamin (riboflavin). FADH, is a necessary cofactor in some special dehydrogenase enzymes that we call flavoproteins, which are found mainly in the mitochondria. There they play a crucial role in the part of the energy turnover we call cell respiration. (You can read more about that in Chapter 4.) Flavoproteins are a different group of dehydrogenase enzymes than those that have NADH and NADPH as a cofactor. We must look more closely at NADH, NADPH and FADH, as energy carriers.

More complex inheritance patterns

Often the inheritance patterns for traits are more complex than d Mendel described. It is common for a property, e.g. Body height or intelligence, can be determined by several genes. A gene can have more than two alleles. There are other forms of domination than the complete one described by Mendel. This will give other decomposition conditions monohybrid and dihybrid inheritance. Genes that are on the same chromosome are not independently distributed, but are usually inherited together. Because the sex chromosomes are not homologous to both sexes, genes on the sex chromosomes will be inherited in a gender-dependent manner. than described for There are various forms of domination. In the example of flower color on page 178, we have a case of complete dominance. That's because one purple color allele is sufficient to produce enough dye. In this and similar examples, the recessive gene is mutated (see page 194) relative to the dominant and will not cause protein to function. In order for the recessive phenotypes to be expressed, the gene pair must be mutated on both chromosomes. In some cases, mutated genes can lead to disease. If the healthy gene is completely dominant over the mutant, only individuals homozygous for the mutated gene will be affected by the disease.

Cloning of organisms

On July 5, 1996, the Dolly sheep came to the world. Dolly was the first teddy bear who was a clone (genetic copy) of an obese individual. Later, mice, cows, pigs, cats, goats, horses, rats, dogs and several other animals have been cloned. Trout pig has not been monkeys or humans cloned, but this may soon change cee. The method used to make Dolly is called somatic cell nucleus Suruofiano When cloning with somatic cell nucleus transfer, the nucleus of an unfertilized egg is first removed. Then, a nucleus from a very ordinary body cell (called somatic cell as opposed to a germ cell) from the animal to be cloned is inserted into the (nucleated) egg. If the nuclear transfer is successful, the ezzet will be as after a normal fertilization with a sperm. Dolly, named after American country singer Dolly Parton, was cloned from a developing cell nucleus taken from a cell in the udder of an adult sheep. You can read more about the Dolly sheep on the Bios website. When the cloned embryo is inserted into a uterus so that it can develop into a new individual, we call the procedure reproductive cloning. If, however, the embryo is allowed to develop in the laboratory into a blastocyst to be used for research, the method is often called therapeutic cloning or research cloning. Before one can have hopes of cloning a born individual, one must be able to clone viable embryos. Monkeys managed to clone embryos only in 2007 after several years of trying. Scientists are gaining more knowledge about cloning, and today there is reason to believe that it will be possible to clone monkeys and humans who develop into born, viable individuals if they really put in great resources to make it happen. . However, one issue is whether you, I, and everyone else in society want us to clone monkeys and humans.

Oxidative phosphorylation

Oxidative phosphorylation is the third major part of cell respiration. Here energy from NADH and FADH is transferred to ATP. NADH and FADH, release energy, electrons and H ions. In the oxidative phosphorylation, d. Reactions occur where the oxygen gas is used. It is when oxygen gas reacts with H that originally comes from NADH, and water is formed. Oxidative phosphorylation takes place in the curved inner mitochondrial membrane. The name oxidative phosphorylation tells us that oxygen is necessary and that ADP is linked to P - ie ADP is phosphorylated, and we get ATP. The reaction we describe here for NADH is similar to that of FADH. The electrons from NADH are trapped by special proteins in the mitochondrial membrane. These electrons are transported from protein to protein. They alternate as electron acceptor and electron donor. The reaction is similar to that of the thylakoid membrane of the chloroplasts, photosystems II and I, of the light-dependent reaction. The oxidative phosphorylation is also called the electron transport chain. As the electrons go from protein to protein, energy is released. The energy is used to pump H * ions through transport channels from the innermost space of the mitochondria and into the gap between the two mitochondrial membranes. This reaction produces an excess of positive charges in the gap, a charge difference - voltage - because the gap becomes more positive and the innermost space in the mitochondria more negative. The charge difference between the amount of H * outside and inside the membrane is called a proton gradient (see page 86). In the inner membrane are also transport channels with ATP-enzyme enzymes. The charge difference between the inner compartment and the gap in the mitochondria causes the H ions to be released through the transport channels and go from the gap to the inner compartment. At the same time, energy is released, This energy is used in the reaction where ADP and phosphate groups form ATP. The ATP axis catalyzes the reaction. The H ions, which are now in excess in the innermost space, are coupled to oxygen gas, and together they form water molecules. Oxygen is thus used only when we arrive at the last partial reaction in the aerobic decomposition. It is the supply of oxygen that "drives" the reaction further, because H from the cleavage of NADH is removed and ATP is produced. Lack of oxygen stops the reaction and then ATP is not produced. The energy yield of aerobic glucose degradation In the third body of the aerobic cell respiration, the oxidative phosphorylation, energy is transferred from NADH and FADH to ATP. It is difficult to calculate how much energy can be transferred from a molecule of NADH or FADH to ATP, ie how many ATP molecules can be built using the energy of NADH and FADH. Generally, we assume that the energy in two NADH can generate five ATPs, while the energy in two FADHs is enough to generate three ATPs. The two NADH formed in the cytosol by the glycolysis must be transported through the mitochondrial membranes, where the energy from NADH can be transferred to ATP. Transport is an active transport, ie it is energy intensive. Earlier, it was assumed that it cost "one ATP per two NADH" to get them through the membrane. But it has turned out that the amount of energy required is very small. Therefore, the total energy yield is approx. 32 ATP. In earlier calculations, the energy yield of cleavage of a glucose molecule was measured at 36 ATP, but more recent calculations indicate a slightly lower yield. Whether the correct number is 36 or 32 is difficult to calculate.

Copying of DNA by PCR

PCR is an abbreviation for polymerase chain reaction, called the technique in Norwegian. This is a technique for making an enormous number of copies of a specific DNA sequence, up to a few tens of thousands of base pairs. Until the invention of PCR, the only method that produced a large number of copies was: the desired DNA was inserted into plasmids. The plasmids were transferred to bacterial cells which were then cultured in large quantities. Thereafter, the plasmids were isolated from the bacterial cells. Plasmids are small circular chromosomes that the bacteria have in addition to their main chromosome. The plasmids in the bacterial cell are also copied. The plasmids are not necessary for the bacteria, but they often contain genes that encode antibiotic resistance. To perform a polymerase chain reaction, we must have two DNA primers that are complementary to the ends of each DNA strand on the DNA to be copied. The primers are short pieces of DNA which are necessary because the DNA polymerase can only make DNA from the end of an existing thread. On page 138 you could read about RNA primers. DNA primers work in exactly the same way, but there is a difference in that DNA primers are more stable and do not break down as easily as RNA. Synthetic DNA primers are easy to make. Once the DNA primers have been added, copying can begin, Primers of the desired sequence can be purchased. Single-cell DNA is sufficient as template thread. The chain reaction is carried out in three steps as we know it from normal copying of DNA. You can recognize it from Chapter 5: 1. Double-stranded DNA opens, here by heating to 95 ° C, and is split into two simple template threads. 2. Complementary DNA primers bind to the template threads. 3. DNA polymerase attaches to the template thread and forms new double-stranded DNA. Together, these three steps constitute a round that must be repeated many times in order to obtain large amounts of the DNA bit. For each round, the number of copies of the DNA duplicate is doubled. After 30 rounds, approx. 1-10 ° (1 billion!) Double-stranded DNA molecules. Heat-stable DNA polymerases from bacteria living in hot springs are used. The polymerase chain reaction has revolutionized the work of gene technology by allowing very limited amounts of DNA to produce safe results. The technique is therefore included as an important step in many methods, e.g. in association with the cloning of genes for the production of genetically modified organisms in connection with the production of genetic fingerprints (see page 230), Pi due to the sensitivity of the polymerase chain reaction (needs DNA from only one cell), the technique is very vulnerable to contaminating DNA, in the laboratory or DNA from other samples be copied in place of the DNA from the sample you wish to examine.

Genetically modified plants

Plasmids are also used to transmit genes to plants. The most commonly used is a plasmid found naturally in the soil bacterium Agrobacterium tumefaciens. This bacterium infects many plant species and at the same time transmits DNA. If we insert a selected foreign gene into this plasmid, the gene is transferred to DNA in plant cells infected by the bacterium. If we additionally insert a gene for antibiotic resistance into the same plasmid (or another gene that can be used to secrete the cells that have been inserted) gene), we ensure that only cells that have received foreign DNA can grow on a nutrient medium containing antibiotics. It is relatively easy to create whole plants from specialized cells in plants. Different cell lines the foreign gene inserted can therefore be used to form plants that have the new gene in all their cells. For single-leafed plants (including maize, rice, cereals and grasses), it has been difficult to transfer both genes by bacteria and s to whole plants of specialized cells. For these species, a method called gene canon has been developed. Then plasmids with the desired pe are injected into the plant cells.

Epistasis

Properties may be controlled by several genes. Epistasis is when a gene at one locus, i.e. at one particular site on homologous chromosomes, is suppressed or favored by a gene at another locus, i.e. at another locus. Two homologous chromosomes have the alleles for the same trait at the same locus (see page 176). Therefore, a dominant allele that hides the expression of a recessive allele will always be located in the same location on the corresponding homologous chromosome. An epistatic gene that hides the expression of another gene is always located at a different locus. Even if a child has an allele for brown or blue eyes, this trait will be masked - covered - if merciful to albinism. The gene for albinism lies on another chromogen gene also has that of the eye color genes. Another example is a gene that gives black color to cattle and covers the color brown, which is due to another gene.

Denaturation

Proteins change structure if heated to high temperatures or exposed to very high or very low pH values. D. The coiled protein molecule is first coiled out and then coiled at first coiled. This we call denature but again, different from ring. The word itself may not be known before, but everyone has gone missing. tical examples of what this is: boiling or roasting eggs, fish or cat Also when we put meat or fish in a marinade with a little vinegar or lemon juice, the proteins are denatured. We put meat and fish in sour marinade because the low pH value breaks some bonds in the coiled protein molecules - the meat and the fish are mashed. Enzymes can be permanently destroyed by denaturation. The denaturation is irreversible. That is, the reaction cannot be reversed and go back again. But you know that. An egg may not become liquid again after you have first cooked or fried it.

Replication of DNA

Replication All multicellular organisms have evolved from one cell that has repeatedly split. In addition, cells must be replaced by new ones as they grow old and die. In both cases, one parent cell gives rise to two daughter cells. With few exceptions, all cells in an organism contain the same genetic information, ie copies of the same genetic material. Before a mother cell divides into two daughter cells, all the chromosomes must be copied exactly so that the new cells get as many chromosomes as the mother cell and thus the same genetic information. The process of copying the DNA is called replication. The word really means folding or rolling back. In copying, each of the individual threads in the DNA acts as a template thread. The template thread is a pattern for the new DNA thread. Only nucleotides with bases that are complementary to the bases in the template thread can be included in a new DNA strand. Together with the template thread, these nucleotides form a new double strand. The result of this is that one duplicate thread after completion of copying has given rise to two identical duplicate threads. Each of the new double threads is composed of an "old" template thread and a newly formed thread.

Restriction cutting and ligation of DNA

Restriction cutting is a technique using restriction enzymes that recognize specific short sequences of double stranded DNA and can cut the DNA into these sequences (see the figure below). The enzymes are naturally found in bacteria, where they are tasked with destroying foreign DNA by cutting it into pieces and thus protecting the cell, for example, against viruses. Hundreds of restriction enzymes from different bacteria are 1. DNA sequence that is recognized by a restriction enzyme. 2. The restriction enzyme cuts the DNA sequence between G and A. 3. Part of a DNA molecule from e.g. a plant is cut with the same restriction enzyme and has complementary ends. 4. DNA is glued together using ligases and we get recombinant DNA. identified and are now being produced for sale and use in the field of genetic engineering. By using selected restriction enzymes on known sequences, specific genes or portions of genes from larger DNA molecules can be excised. And by using enzymes called ligases, one can glue clipped genes to other DNA, e.g. into plasmids. This technique is called ligation. With it, it is possible to transmit genes to bacteria, plants or animals to produce genetically modified organisms.

Lethal genes

Some genes have the property that if certain alleles occur in a double dose, they have a lethal effect. We say they are lethal. The coat color of mice can be used as an example. The gray fur (y) allele is recessive to the yellow (y) fur allele. If two heterozygous mice with yellow fur get cubs, cubs with the yy genotype will turn gray, those with Yy will turn yellow, while the cubs given the double dose yellow allele, YY, will die in the uterus. Because these mice die in the uterus, we get different cleavage conditions than expected in normal mono-hybrid inheritance. 25% becomes YY, but dies before birth. Therefore, of the living cubs, 67% (or 3) are yellow and 33% (or 3) are gray.

Codominance

Some properties are inherited in that both properties are expressed simultaneously and not as a mixture as it is in incomplete dominance. Kodominans (co-dominance) we can say is a "both-and". In man there are 21 different blood type systems. ABO and rhesus are two of them. In the ABO system, a human can have the genotypes AA, A0, BB, B0, 00 or AB. Alleles A and B lead to a protein synthesis that produces two special protein molecules on the outside of the red blood cells. AA and A0 have one type, BB and B0 have the other, while AB has both. In this case, a gene has three alleles. Both A and B are dominant, while 0 is recessive.

Dominant and recessive alleles

Some traits in humans are due to only one gene pair. An example of a gene pair is the ability to roll or not roll the tongue together into a tube. We use here the letter T for the ability to roll the tongue g the letter t for not being able to roll the tongue. Because there are two homologous chromosomes, a person can have three different combinations of alleles for this property: TT, Tt and tt. A person with the combination Tt has the allele T on one chromosome and the allele t on the other chromosome. Where the same allele (TT and tt) is found on the homologous chromosomes, we say while saying that individuals with two different alleles that the individual is homozygous, (Tt) are heterozygous. We use uppercase and lowercase letters to signal that one allele is down over the other. The ability to roll the tongue longitudinally into a tube is genetically determined. Eynen says rolling is dominant over not being able to roll. "Tongue rollers" have the allele TT or TT, while "non-rollers" have the allele TT. We say that people who can roll the tongue have two different genotypes: TT and Tt, but they have the same phenotype. The same applies to the free or fixed ear lobes that you read about on the previous page. The shape of the earlobes is determined by two alleles. A dominant allele L provides free ear flaps, while only individuals who are homozygous for recessive L1 have a fixed ear flap that is attached tightly to the head. The genotype tells us which alleles an individual has for a trait, while the phenotype is traits that are expressed. Dominant alleles are expressed in both homozygous dominant (TT) and heterozygous (Tt) individuals. Declining alleles are called recessive, and we write them in lowercase. In our case, the "non-roll" property is recessive, and a person lacking the ability to roll the tongue has the genotype tt. Recessive alleles are thus first expressed in the homozygous recessive (tt) individual, If we now go back to Mendel's pea flowers and the inheritance of ponytail color, we can fill in the figure on page 174 and insert the genotypes uiese Then we see that the inheritance pattern is due to one gene pair which governs the flower colour.

Energy turnover in all living organisms

The Sun is our most important source of energy. On Earth, all energy conversion begins with autotrophic organisms absorbing energy and producing organic matter. fer. Many of the autotrophic organisms perform photosynthesis. In photosynthesis, solar energy, water and carbon dioxide are converted into glucose and other organic compounds. In addition, the autotrophic organisms produce oxygen. So they are producers. The organic compounds that are formed are transferred from link to link in a food chain - from organism to organism - in that the first organism is eaten by another, then the second is eaten by a third, etc. that glucose and other organic compounds react oxygen and form carbon dioxide and water in the cell breath. The organisms that do not produce glucose themselves, and which eat other organisms, are consumers (consumers). We say they are heterotrophic organisms. The division into autotrophic and heterotrophic organisms is based on the answers to these two questions: Who makes the food, and who eats who? The autotrophic organisms make the food, the heterotrophic organisms eat them - and many heterotrophic organisms eat other heterotrophs. Only the autotrophic organisms perform photosynthesis. Both the autotrophic heterotrophic organisms have cellular respiration. The sum of all these processes is called the metabolism or metabolism. You can read more about photosynthesis in the ones where chemical reactions release or take up energy and building blocks, chapter 3 and cell respiration in chapter 4. The figure in the margin shows how energy is transferred in an ecosystem.

Anaerobic cell respiration

The anaerobic degradation of glucose produces much less energy than the aerobic, but the organisms that drive anaerobic degradation of glucose nevertheless receive a certain energy yield. Many organisms die if they enter an aerobic environment. They can only live in an anaerobic milia or anaerobic degradation. Most pro- and eukaryotic organisms have aerobic cell respiration because they provide more energy than the anaerobic, but they may have anaerobic degradation there as they have poor oxygen supply. Still, this is only a temporary solution. For mammals, such a solution can only last for a few minutes. The lack of oxygen gives too little ATP to the cells, we feel discomfort, and then we can faint and possibly die. When an organism that normally has aerobic cell respiration switches to anaerobic cell respiration, the lack of oxygen will cause the oxidative phosphorylation to stop, pyruvic acid does not enter the cancer cycle, and pyruvic acid must be further cleaved. The products vary with the different organisms. Some produce carbon dioxide at the same time, others do not. For example, in lactic acid bacteria and yeast fungi, there are enzymes adapted to anaerobic degradation of pyruvic acid. The enzymes in them are different, and the degradation products are different: e.g. lactic acid or ethanol. All anaerobic decomposition we call fermentation or fermentation, also the lactic acid production that takes place in our muscles when we get too little oxygen. The word fermentation is used in everyday speech about what happens in the dough when we bake bread, when a brewery allows grains to ferment, or when grapes ferment to wine. A beer producer or a wine farmer often uses the term fermentation. We are talking about the same process either call it fermentation, fermentation or anaerobic decomposition. Prokaryotic organisms do not have mitochondria, but they may have indentations in the cell membrane that make the membrane surface larger. The enzymes necessary for the degradation of glucose and the further degradation of pyruvic acid are attached to the cell membrane. In organisms that degrade glucose anaerobically, glycolysis takes place just as in those who have aerobic degradation. Therefore, we do not repeat this process here.

stem cells

The cells in the body have a limited lifespan, and cells that die are replaced by new ones in healthy individuals. It is estimated that adult humans have 12 million new blood cells. It is the stem cells that are responsible for this huge production of cells. Stem cells are likely to be found in all tissues and organs of the body. When a stem cell divides, both new stem cells and progenitor cells can be formed. The precursor cells divide quickly, over and over again, producing a single second of 17 million new cells. Of these, e is a supplier. Eventually, the new cells begin to specialize, and eventually get specialized (mature) cells. We say that cells differentiate tracheal cells via precursor cells into specialized cells. Examples of specialized cells are formed by thousands of cells all originating from the same are nerve cells, red and white blood cells, skin cells and muscle cells. While there are very many specialized cells in the body, there are very few stem cells. An example: In the bone marrow, there are stem cells that form blood cells. The stem cells that make blood cells make up only about 0.01% of the total number of cells in the bone marrow. In all body tissues and organs there is a need for new cell formation. The stem cells are responsible for this, and today assume that there are about 20 different types of stem cells in adult individuals. The stem cells often have names after where they are Jert from. For example, we have bone marrow stem cells (isolated from the bone marrow), nerve stem cells (from the brain), muscle stem cells (isolated from muscles), embryonic stem cells (isolated from fetuses), embryonic stem cells (isolated from embryo), etc. The stem cells known most well, is in the bone marrow and makes blood cells. Since the 1950s, research has been done on stem cells that make blood cells. Today we have methods for isolating them and cultivating them outside the body, and we know a lot about how their production is regulated in the body. Stem cells differ from other cell types in several ways. First, they are unique in that they can divide and give rise to new stem cells. This makes the stem cells sely if they divide. In other cells that divide into two, neither of the two new cells formed will have exactly the same properties as the cell they came from, even though they have the same inheritance. Second, the stem cells are unspecialized (immature) and can produce several different types of cells. For example, a stem cell that makes blood clays can produce all the different types of blood cells found in blood red and white blood cells and platelets. Nerve stem cells can produce any type of nerve cells, skin stem cells all types of skin cells, etc. These are un so different from specialized cells, which can only produce one type of cells.

Linked genes and cross-over

The condition that gene pairs can be inherited independently of each other is that they are on different chromosome pairs. Today we know that the different chromosomes in humans contain from hundreds to almost three thousand genes. Genes that are on the same chromosome are called linked genes and together form a linking group. The number of coupling groups corresponds to the haploid chromosome number in an organism. Man has 23 linkage groups. Genes within the same linking group are usually inherited together. This means that we get different cleavage conditions when we follow two linked gene pairs than it does with normal dihybrid inheritance of genes that are inherited independently. As an example, we can imagine that the characteristics of seed shape and seed color in Mendel's peas were linked genes, which is why they are not in reality. What splitting conditions would we then have if plants that were homozygous for the dominant traits round / yellow seeds were crossed with plants that were homozygous for the recessive traits wrinkled / green seeds? In the Fl generation we would have received only round and yellow peas with RrGg, as Mendel got when the genes were distributed independently For the difference would have come when the Fl generation was crossed with themselves the Fl generation would have given only germ cells with two different allele combinations: RG and rg: The F2 generation would therefore have yielded only two phenotypes of round / yellow seeds and wrinkled / green seeds in a ratio of 3: 1. Fully coupled gene pairs are inherited as if they were one gene pair, ie as in monohybrid ary. the genotype If we conduct a test cross (see page 180) between an individual who is heterozygous for two dominant alleles, with an individual who is homozygous for the recessive alleles for the same gene pair, we expect offspring with parental phenotypes in the ratio 1: 1. When a larger ata such crossings are carried out, the ratio does not become 1: 1. In addition the parent types we get new combinations of the two gene pairs. We remember from the previous chapter that the meiosis usually crosses homologous chromosomes (see page 146). This means that one or more parts of a chromosome swap with parts of the homologous chromosome. This gives germ cells with different combinations of alleles than we expect from linked genes. When these germ cells are combined with recessive alleles in new individuals, new phenotypes called recombinants are revealed. They Bar other combinations of alleles than the parent types. Coupled genes and overcrossing were discovered by American Thomas Hunt Morgan when he attempted banana flies (Drosophila melanogaster). Banana flies with normal phenotype (wild type) have gray body color (G) and long wings (V). A mutant form has black body (g) and short wings (v). Wild-type alleles predominate over the mutant alleles. By making repeated crosses of a heterozygous wild type (GgVv) with a homozygous mutant (ggvv), Morgan wanted to investigate whether the body color and wing length genes were linked or not. If the genes were on different chromosomes, he could expect to have four types of offspring: gray body / long wings, gray body / short wings, black body / long wings, black body / short wings in a ratio of 1: 1: 1: 1. If, on the other hand, the genes were on the same chromosome, ie linked, the expected result would only be offspring of the same type as the parents, ie gray body / long wings and black body / short wings in a ratio of 1: 1. As a result, Morgan got that both types of parents were represented in a large and almost equal number. This interpreted Morgan as having the body color and wing length genes on the same chromosome, ie linked genes. But in addition to the parent types, flies were also found with two new combinations of properties, so-called recombinants (see the figure on the next page). This showed that there had been a crossover between two homologous chromosomes in an area of ​​the chromium that lies between the genes for body color and wing length. germ cells with different combinations of alleles than we expect from linked genes. When these germ cells are combined with recessive alleles in new individuals, new phenotypes called recombinants are revealed. They Bar other combinations of alleles than the parent types. Coupled genes and overcrossing were discovered by American Thomas Hunt Morgan when he attempted banana flies (Drosophila melanogaster). Banana flies with normal phenotype (wild type) have gray body color (G) and long wings (V). A mutant form has black body (g) and short wings (v). Wild-type alleles predominate over the mutant alleles. By making repeated crosses of a heterozygous wild type (GgVv) with a homozygous mutant (ggvv), Morgan wanted to investigate whether the body color and wing length genes were linked or not. If the genes were on different chromosomes, he could expect to have four types of offspring: gray body / long wings, gray body / short wings, black body / long wings, black body / short wings in a ratio of 1: 1: 1: 1. If, on the other hand, the genes were on the same chromosome, ie linked, the expected result would only be offspring of the same type as the parents, ie gray body / long wings and black body / short wings in a ratio of 1: 1. As a result, Morgan got that both types of parents were represented in a large and almost equal number. This interpreted Morgan as having the body color and wing length genes on the same chromosome, ie linked genes. But in addition to the parent types, flies were also found with two new combinations of properties, so-called recombinants (see the figure on the next page). This showed that there had been a crossover between two homologous chromosomes in an area of ​​the chromium that lies between the genes for body color and wing length.

the krebs cycle

The further cleavage of pyruvic acid occurs at different sites in prokaryote and eukaryotic cells, and it differs depending on whether the organisms have access to oxygen or not. Another reason for the further cleavage varies is that the organisms produce different enzymes and the reactions take different paths. The figure at the top of the next page shows a simplification of glycolysis together with aerobic and anaerobic cleavage of pyruvic acid. In section 4.3 we look at anaerobic cleavage of pyruvic acid. The kreb cycle is the second major part of the aerobic cell respiration. We follow one pyruvic acid molecule further, although each glucose molecule produces two pyruvic acid. Therefore, when we look at the energy yield further, it must be doubled when we are to sum the total energy yield by the breakdown of one glucose molecule. Here we will look at the cleavage of pyruvic acid into eukaryotic organisms that all have mitochondria in the cells. The mitochondria stay, too called the "power plant" in the cells, because here the chemical reactions that c give the energy that is used when ADP and P form ATP. The mitochondria are surrounded by a double membrane. The outer membrane is smooth on the inside is curved to give it a large surface. The pyruvic acid molecule is so small that in eukaryotic organisms it can pass through the mitochondrial membranes by diffusion and enter the innermost space of the mitochondria. Then it goes into the sub-reactions of the cancer cycle. As the pyruvic acid molecule (3C) enters the crayfish cycle, it is cleaved by a carbon dioxide molecule (1C). This reaction releases some energy into the formation of one NADH. The "residue", a two-carbon compound (2C), is coupled to a coenzyme called coenzymeA and we get acetyl-coemzymA (2C). Acetyl coenzyme enters the cycle where the two carbon compound reacts, and coenzyme loosens and can then be reused. We can say that coenzyme acts as a carrier for the two carbon compound - into the crayfish cycle. The cancer cycle consists of many part reactions that go on cycle because the first part reaction starts with oxaloacetic acid (4C), which was a residue after the previous round, attaches to acetyl-coenzyme A and water and enters a new round of part reactions. The product of the first partial reaction is citric acid (6C). The cancer cycle is also called the citric acid cycle, after the first partial reaction in which citric acid is formed. In two new partial reactions, two carbon dioxide molecules (1C) are decomposed from citric acid (6C) and we get succinic acid (4C). The structure of the four-carbon compound is rebuilt several times, in several steps, from succinic acid (4C) to fumaric acid (4C), on to malic acid (4C), without being decomposed by carbon. one molecule of water. The structural changes from succinic to oxaloacetic acid cause electrons, H ions, phosphate and released energy to be used to form energy-bearing compounds: one molecule of ATP, one molecule of FADH, and one molecule of NADH. The net reaction of degradation of one pyruvic acid molecule is: pyruvic acid + coenzyme + 4 NAD + FAD + ADP + P + 2H, O - coenzyme + 4 NADH + FADH, + ATP + 3CO. of the krebs cycle.

From mRNA to functional protein translation

The information contained in DNA and RNA in the order of four for different bases is translated into another language in the translation. It consists of 20 different amino acids which are the building blocks of proteins. The information in the base sequence is translated into protein based on a code consisting of three bases, a triplet. Series of triplets constitute "words" on three and three bases, and they are translated into a corresponding series of amino acids. Triplets of mRNA bases are called codons and read in the 5'-3 'direction. It is also in this direction that mRNA sequences are written in. The relationship between the codons and the amino acids they encode, we call the genetic code. There are 64 possibilities for combining codons of the four bases. Thus, there are 64 different codons encoding 20 amino acids. In other words, there are more codons than there are amino acids. Therefore, most amino acids have multiple codons. The amino acids methionine and tryptophan are an exception. They only have one codon. In addition to coding for the methionine, the codon AUG also acts as a start signal for the translation of mRNA into proteins. Three codons do not encode amino acids, but act as a stop signal and mark the end of the genetic message. No codons encode several different amino acids. Therefore, We say that the genetic code is unambiguous. The same genetic code is used in other living organisms. We therefore say that the code is universal. It is thus a language that applies to all known life. Finished mRNA containing the genetic code, along with tRNA and a ribosome, constitute what we might call the translational machinery.

The food contains macro and micronutrients

The macronutrients in the food are fat, carbohydrates, proteins and water. They make up most of the food. The micronutrients are primarily vitamins and minerals. All food packages must have a product declaration showing what they contain of the various nutrients and how much energy there is in them. At the same time, the pack should have a warning for allergy sufferers if it contains, for example, nuts, gluten or milk. All food, olive oil and chocolate, broccoli and pork chops etc. contain varying amounts of macro and micronutrients. We divide the nutrients into six categories: • fat carbohydrates proteins water minerals vitamins The first four categories are considered macronutrients. We need quite a large amount of them, and our bodies are largely composed of these substances. Living organisms consist of 60-98% water. Minerals and vitamins are micronutrients and we need little of them, just a few milligrams or grams per day is enough. You may find it strange that we consider water as a nutrient. We call it a nutrient because water is absolutely necessary. We can survive for a few weeks without food because the body has long-term stores of fat and carbohydrates, but we die after a few days without water because most metabolic processes depend on water and because the processes where the waste substances are to be removed are largely in the aqueous environment of the cells, blood, urinary tract and intestines. Every day we should get at least 2.5 liters of water, either as a drink or through the food. Since different foods have different nutrient content, it is important to have a varied diet. A diet with just broccoli or just chocolate becomes - as you probably know - too one-sided. The energy content of food varies widely. The content of building blocks needed by the body also varies. The energy content of food is a measure of how much energy can be released in the chemical reactions that happen in the body when the food breaks down in the cellular respiration. Some foods contain a lot of energy without necessarily containing as many necessary building blocks. Let's compare the energy content of four different foods (see table in the margin). We specify the energy content in joules, J, or in kilojoules, kJ. 1000 joules = 1 kilojoule. From the energy content alone, it can be difficult to say anything in particular about how healthy or unhealthy a food is. For example, olive oil contains a lot of healthy fats and should be part of the diet despite its high energy content. Alcohol is considered in some listings with the nutrients, not because we need alcohol, but because alcohol has a very high energy content.

Comparison between mitosis and meiosis

The main difference between mitosis and meiosis is that while mitosis provides diploid (2n) daughter cells with the same genetic information as the morcell, meiosis provides haploid (n) daughter cells with half the chromosome set and with genetic information that is different from the parent cell. Diploid cells that have arisen as a result of mitosis still contain homologous chromosomes, ie chromosome pairs. In the meiosis, on the other hand, the homologous chromosomes are randomly distributed among the four haploid daughter cells, and the cells contain only single chromosomes. Because the genetic information in two-parent homologous chromosomes is not identical, the genetic information in the haploid germ cells differs. The two types of cell division have different function and different results. Based on a fertilized egg cell, the mitosis creates multicellular adult individuals and produces new cells for growth and repair. Mitosis can also contribute to unfamiliar reproduction. Meiosis produces germ cells with tic variation between the cells. The genetic variation in the germ cells is further increased by the occurrence of overcrossing in the meiosis, which does not occur in the mitosis.

The pH value affects the reaction speed

The pH value, the acidity, is a measure of the amount of H, O "ions in the solution. The charged H, O * ions affect the bonds that determine how the polypeptide chain in the enzyme is coiled. An enzyme works optimally at a particular pH value. The activity of the enzyme varies with the pH value. If the pH becomes too high, the enzyme can be denatured. In most of our body cells, the pH value is 5.5-7 (about neutral ), and this value is optimal for the enzymes inside the cells. The enzyme trypsin then cleaves the peptides to amino acids in the small intestine Optimum pH value for trypsin is about 8. Many species of arches have enzymes that are most effective at a pH of 2 or lower.

The replication machinery

The prerequisite for the copying of the DNA to start is that the double strand is opened. Specialized proteins recognize the starting points of replication and separate the two DNA strands. Then the bases in the template threads become available for enzymes and nucleotides with complementary bases that provide the structure of the new single threads. This occurs at special starting points in the double thread. The copying assumes that specialized proteins recognize the starting points for replication. These proteins bind to copying and form a complex. This protein complex with enzymes and DNA works together as a "replicator". This replicator uses ATP as energy. We will take a closer look at enzymes that are needed on some of the parts of this machine. A replication stack is formed at the starting point where the double strand DNA is opened. The replication bubble consists of two replication forks together with the newly formed double stranded DNA between the two replication forks. The replica bubble will expand in both directions of the double strand from the starting point. so that the entire DNA molecule is copied. In the circular chromosome in bacteria, there is one starting point. In eukaryotic cells, on the other hand, there are hundreds or thousands of such starting points where the double strand opens in the white chromosome. At each starting point where the double strand is opened, there is thesis, ie, formation, of new DNA. Due to the Y-shaped structure where the double strand is opened, this area is called a replication fork. Hydrogen bonds usually hold the two strands of the double strand together. Enzymes open the double strand by breaking the hydrogen bonds between the bases and twisting up the DNA. DNA polymerases are enzymes that synthesize new DNA by attaching nucleotides to the growing end of the new single DNA strand. In the bacterium E. coli, two different DNA polymerases are involved in the copying of DNA. At least eleven different DNA polymerases are known from eukaryotic cells. DNA polymerases cannot initiate production of new DNA from a template thread alone. They can only extend the end of an already started thread. This problem is solved by an enzyme called primase making a short RNA strand of about 10 nucleotides. This short thread we call an RNA primer. The RNA primer is complementary to the template thread to be copied. The DNA polymerase then binds to the RNA primer and initiates production of new DNA by attaching nucleotides to the 3 'end of the primer. The RNA primer is then removed from the DNA. In order for the daughter cells to contain the same genetic information as the parent cell, the copy of the genetic material must be very accurate. As little as one error per 10 ° of copied bases has been observed for the mammalian genetic material. Such accuracy is only possible because the DNA polymerases have a proofreading function. During the replication, the DNA polymerases compare the base of each new nucleotide with the base of the template nucleotides. Nucleotides that do not form complementary base pairs with templates is quickly removed. In addition, the cell uses other specialized enzymes to remove errors that have escaped the review or have occurred since. During copying, the DNA strand grows by about 500 nucleotides per second in bacteria clay such as human cells. That the rate is lower in eukaryotic cells may be due to the DNA being wrapped in proteins. and with 50 nucleotides per second of eukaryotic cell.

Mitosis

The process that causes each of the daughter cells to have the same genetic information as the mother cell is called mitosis. Here we will take a closer look at mitosis in multicellular eukaryotic organisms. Mitosis occurs in body cells when multicellular organisms grow and when cells need to be replaced. Many (but not all) multicellular organisms have body cells with a double set of chromosomes such that two and two chromosomes form a chromosome pair. One set of chromosomes in humans will consist of 23 chromosomes, that is, chromosomes from 1 to 22, and in addition a sex chromosome. The germ cells have a single set of chromosomes. They are haploid and are termed n. A double set of chromosomes (one from father and one from mother) are the result of gendered reproduction. Cells with such a double set have 46 chromosomes. We call them diploid cells and denote them 2n. A chromosome pair that has the same size and content of genes is called homologous chromosomes. Two homologs chromosomes are not identical, as they may contain different variants (alleles, see page 177) of the same gene. While one chromosome contains the gene for free earlobe, the other chromosome may contain the gene for solid earlobe. Cells that carry the mitosis have copied their DNA. Each chromium then consists of two identical DNA molecules, what we called sister chromatids. In the mitosis, the nucleus of one diploid cell with two identical sister chromatids in each chromosome is divided into two diploid cell nuclei with a chromatid in each chromosome as the figure below shows. This happens through several phases. We divide the mitosis into the five phases of prophase, prometaphase, metaphase, anaphase and telophase. Subsequently, a cytokinesis (two-division) occurs, which means that the two daughter cells are physically separated.

From mRNA to protein

The translation begins by suggesting that the small portion of riby stain binds both mRNA and the tRNA that binds amino acid methionine and which has anticodon UAC. The small ribosome portion moves to look along the mRNA until it finds a start codon (ALIG) that can bind to the tRNA via the anticodon. Therefore, arminoic acid methionine will always be the first in the polypeptide chain. Then the major part of the ribosome attaches. A polypeptide is formed by transporting amino acids bound to tRNA into the ribosome and binding From mRNA to protein to the preceding amino acid. When two tRNAs are tested at each site of the ribosome, a peptide bond forms between the last amino acid in the growing polypeptide chain attached to one tRNA and the new amino acid attached to the last arriving The tRNA The correct translation is ensured by bringing the amino acids into the ribosome by means of a tRNA with an antibody that is complementary to the codon of the mRNA. The ribosome then moves in a 5-3 direction along the mRNA wire one to a stop codon (UAG, UAA or UGA). No tRNA was able to bind to the stop codons. When the ribosome came. more to a stop codon, the polypeptide chain of the tRNA loosens. Then, the ribosome detaches from the mRNA. A polypeptide consists of many, often several, thousands of amino acids bound together in a chain. It is common for multiple ribosomes to attach to the same mRNA once the previous ribosome has moved away from the start codon. The ribosomes are left as beads on a string and enable rapid production of large amounts of protein from the same mRNA. It is the structure that determines what function a protein has. The structure of the proteins is formed by the polypeptide chain coiling and folding and then being released into the cell. In order for the protein to be able to do its job in the cell, the polypeptide chain must in many cases be changed. In some cases, certain amino acids or larger portions of the polypeptide chain are removed by enzymes in the cell. In other cases, cofactors, often metal ions or coenzymes (organic compounds), must bind to the protein, or different polypeptides must bind to each other to form a protein with a specific function. In addition, certain proteins may only migrate after other molecular types, for example, sugar, fat or phosphates, are attached to the polypeptide chain.

Complementary base pairs: AT and GC

The two single strands of DNA are held together by hydrogen bonds between the bases at each step. These are far weaker bonds than the covalent bonds that hold the nucleotides in each single strand together, and they provide that a double strand can easily be divided into two single strands by enzymes in the cell. Such divisions of the double strand occur constantly when DNA is to be copied or read. However, the double strand is usually held together well and the structure is stable. The prerequisite for a bond between the individual threads is that the bases on each thread form complementary base pairs. There are only two possibilities for the four bases to form complementary base pairs. Adenine always forms base pairs with thymine, and guanine always forms base pairs with cytosine. This is due to the structure of the bases, and this gives the double wire a uniform diameter of 2 nm (= nanometer). The bases C and T consist of one ring structure, while A and G are larger and consist of two compound ring structures. Two hydrogen bonds are formed between bases A and T and three hydrogen bonds between bases G and C. In this way, the strands of DNA molecules become complementary. We can therefore predict the order of the bases along one thread when we know the order of the other thread. As we shall see later, this is very much in the way of copying DNA.

What has genetic technology given us?

The use of genetic engineering opens up many possibilities, and today there are many examples of genetic engineering products in the form of genetically modified plants, animals and microorganisms. Constantly new ones are being made, and you can always read in newspapers and the Internet about something new that has happened in the field of genetic technology. Some genetic engineering products are at the experimental stage and not put into production. Need and demand, attitudes of the population, national and international laws, regulations and agreements, technological solutions, alternative production methods and price - all of this can help determine what is produced on a large scale. All of the aforementioned factors can be changed quickly and provide a basis for starting production of some GMO products or stopping production of others. In the production of medicines, genetic modification is of great importance, especially because some proteins can be used as medicine directly. "Healthy" proteins with normal function can be produced and replace the "diseased" inactive proteins that some patients make. This is especially true for small proteins like hormones. Hormones are normally produced in limited quantities, and in the past we had to use large amounts of animal organs to extract hormones. Protein recovered animals can in some cases be so different from similar hormones in humans that they cause allergic reactions, and hormones derived from human organs carry the risk of transmitting viral diseases. One of the first commercial products from the genetic engineering industry was the hormone insulin. It is a small protein with 51 amino acids. Insulin lowers blood sugar levels, and lack of or impaired insulin function in the body is the cause of diabetes (diabetes). The gene for insulin was cloned from a human, transferred to the bacterium E.coli and put into production in 1983. The genetically modified bacterium could easily be grown, and insulin was thus able to produce in large quantities. Since more than 60 million people in the world suffer from diabetes, the need for insulin is high, and today it is covered by genetic engineering. Human growth hormone can be produced in large quantities by means of bacteria. It can be used to treat short growth, including in connection with Turner's vynl strap (page 203) in children. Another exerople of a protein product for medicinal use is human lottery factor VIII, which helps blood coagulate and is used to treat bladder disease (haemophilia). Vaccines can be safely and effectively produced using gene modifiers. tea organisms Traditionally, vaccines have been killing or weakening microorganisms, e.g. virus, which is injected into the people to be vaccinated. The body's immune system can recognize proteins on the surface of the attenuated viruses, secreted antigens, and then produces antibodies that match the antigen, and in addition, memory cells. This means that we become immune to vinegar the next time it enters the body, because then our immune system is already prepared for such a viral infection. Even attenuated microorganisms can be dangerous, or the infectious agent can be vaccinated so that it does not produce an immune response. There is a weakness to traditional vaccines. Therefore, the use of genetically engineered vaccines can be much safer. In order to activate the body's immune system it is sufficient in vaccines with non-disease-causing parts of micro-organism. We can achieve this by taking a gene that encodes the antigens in the dangerous microorganism, and clones (see page 234) it into a harmless microorganism that we then use for vaccine. The harmless microorganism thus gets these antigens on the surface. The body then produces antibodies and memory cells that will later recognize the disease organism. Many such vaccines have been made against viruses, bacteria and parasites. For several diseases, vaccines have been developed using genetically modified organisms. The table shows examples of some such diseases from viruses, bacteria and parasites against which vaccines have been prepared. DNA vaccines are a further development of genetically engineered vaccines. Then the DNA encoding antigens for a disease-causing microorganism is injected directly into the organism to be vaccinated. This DNA is then taken up by the cells. They express the antigen of the microorganism, but without the presence of this microorganism The organism's immune system then creates antibodies against the microorganism and will then recognize the foreign antigen and develop immunity that protects the vaccinated organism. DNA vaccines are still mostly at the research stage. As of today (2013), there are four approved DNA vaccines for animals. For humans, no one is on sale, but now DNA vaccines are being clinically tested on humans. There are a number of different diseases It is also possible to produce pharmaceutical products to be used for the treatment of humans, in other organisms. For example, genetically modified sheep produce milk with the protein alpha-1-antitrypsin in large quantities. This protein is used to treat the disease cystic fibrove Genetically modified sheep can also make the protein human blood factor VIII It is then purified from the milk, Plants that are genetically modified can also be used for the production of medicines and vaccine. When genes from pathogenic organisms are cloned into plants and we eat these plants, our immune system is activated so that we become immune to the disease organism. In this chapter, we will look at some of the opportunities and challenges that biotechnology techniques provide.

Bone marrow transplants and umbilical cord blood

There are high hopes today that stem cells could be used to treat a wide range of diseases. But it is far ahead, and today only stem cells from born humans are routinely used for treatment. The most well-known treatment with stem cells is bone marrow transplantation. It was first used in 1968 under the leadership of E. Donnall Thomas. He was awarded the Nobel Prize for his work. Bone marrow transplantation can be used in the treatment of some cancers. They proceed just like this: Doctors take out stem cells from the patient's own bone marrow and store them in a freezer. The cells can be stored for years if frozen to minus 196 C (using liquid nitrogen). The patient is then given a powerful treatment where the goal is to kill all the cancer cells. Such treatment may be radioactive radiation or chemotherapy (chemotherapy). One side effect of this treatment is that even the bone marrow stem cells that make blood cells are killed. Without stem cells that produce blood cells, the patient will die from infections or bleeding within a few weeks. The stem cells that were removed from the patient for the treatment are therefore reset after the treatment to produce new blood cells. If the patient's own bone marrow contains cancer cells, the bone marrow of another human being of the same type of tissue, a donor (donor), is needed. If not, you risk giving cancer cells back together with the stem cells. For all transplantation of living cells, tissues and organs it is important that what is transplanted is not repelled by the recipient's immune system. That is why one is searching for donors who have a tissue type that is sufficiently similar to that of the patient. In many countries, including Norway, there are registers of people who will voluntarily provide bone marrow should a patient, somewhere in the world, need their exact type of tissue. Worldwide, a total of 20 million (2013) people are now registered as possible donors for bone marrow cells. In addition, blood from approximately 560,000 umbilical strands is stored in public blood banks in various countries of the world. Umbilical cord blood contains blood-forming stem cells that can be used in almost the same way as bone marrow stem cells. A large number of donors are needed because the likelihood of finding a suitable donor is small. In Norway, there are about 80 patients each year who, due to severe patients with northwestern European origin, find a donor with a relatively similar tissue type in the bone marrow donor registries and umbilical cord blood. Lean to more than 95% of patients. For patients with a non-European disease, transplantation of blood-forming stem cells needs. For background, the situation is more difficult, and only to a small proportion of d is a suitable donor or umbilical cord blood found. This difference is partly due to the fact that people with a non-European background are only to a lesser extent represented in the bone marrow donor registries and umbilical cord blood banks, and it is therefore considerably more difficult to find a donor or umbilical cord blood with sufficiently similar veys type for these patients. Studies of people who had been treated with embryonic stem cells were first performed in 2010. Nerve cells developed from embryonic stem cells were then given to patients who had recently become paralyzed as a result of spinal cord fractures. However, these studies were discontinued shortly after, and the company that funded the experiments later sold all its work on embryonic stem cells. There is reason to believe there will be more such studies in the years to come.

Factors affecting enzyme activity

There are many factors affecting enzyme activity. Reaction rate increases proportionally with the amount of substrate and enzymes until all & active sites on all enzyme molecules are filled with substrate. Other factors that can make the reaction go faster or slower are varying temperatures or varying pH values.

How stem cells are isolated and cultured

There are several different ways to isolate stem cells. The choice of method depends on the type of stem cell you are looking for, how many stem cells you want to get out, what the star cells will be used for, whether there may be other cell types with the stem cells, and whether stem cells are to be isolated from humans or animals. When isolating stem cells, properties such as SAlmier stem cells from other cell types are utilized. It may be the cell density - that the cells have or do not have specific molecules on the cell surface - that the cells are able to perform under specific culture conditions in the laboratory. Cell density is mainly determined by how much cytoplasm a cell has and how compact the nucleus is. High cytoplasm and low compact nucleus give low density, while low cytoplasm and compact nucleus lead to high density. Stem cells often have little cytoplasm and a medium compact nucleus. For example, molecules on the surface may be different receptors for growth factors that regulate the growth of stem cells. Here we describe how stem cells that produce blood cells can be isolated from the bone marrow. In humans, bone marrow stem cells can be isolated by inserting a needle into the bone marrow in the hip and extracting cells. Another way is to first give syringes with the protein G-CSF (granulocyte colony-stimulating factor). This protein causes many stem cells to leave their place in the bone marrow and enter the bloodstream, so they can be isolated directly from the blood in an advanced centrifuge. This method is widely used to remove stem cells from the bone marrow in humans. In mice, another method is often used. The mouse is killed, and then the entire femur is dissected and crushed to remove all the stem cells in the bone marrow. When stem cells are isolated, there are several different ways they can be grown. However, it is important to note that we have not yet learned to grow all types of stem cells. What often happens is that they differentiate and produce mature, specialized cells instead of remaining as stem cells. After the stem cells are isolated, they are most often placed in plastic bottles or small wells in plastic trays, with a culture medium added. This medium is specially made so that the stem cells thrive. The medium must, among other things, contain the necessary nutrients for the stem cells to live. In addition, various growth factors that are needed to keep stem cells alive are often added. The cells are grown in incubators, which ensure that the temperature is 37 ° C. All work on cells to be grown in the laboratory must be handled sterically to avoid bacteria and fungi.

Why clone?

There are several reasons why scientists today want to clone. For example, cloning can be used as a tool for research into the future treatment of patients and to give birth to cloned individuals. This Why clone? applies to both animals and humans. In the research, cloning of both stem cells living individuals can be used for different purposes. When researching human disease, test animals with the same or similar disease may be useful in research. Of the mammals, mice and rat are most commonly used as laboratory animals. In some cases, however, larger animals such as pigs, dogs and monkeys are needed. These are animals that take a long time to multiply in sufficient numbers, and cloning can therefore be used to obtain in a short time many genetically similar individuals that can be used in research. Cells to be transplanted to a person must be adapted to the recipient's immune system. If not, the cells will be repelled (killed), or the recipient must take medications that inhibit the immune system for the rest of their lives. It may be possible to make cells similar to the patient's own cells by cloning out pluripotent stem cells from the patient. The idea is that from these stem cells you can get ordinary cells that can be used in treatment. Cells made in this way will be genetically similar to the recipient's cells, so there will be no problem with repulsion of the transplanted cells. Nobody has yet managed to isolate stem cells from cloned human embryos - Not everyone wants to try it either. As is well known, there is great opposition to human cloning, and Norway and a number of other countries have banned human cloning. It is also possible to make two genetically similar individuals using a method called embryo splitting. This method involves dividing an embryo in the first days after fertilization, and then each part can develop into a new individual when implanted in a uterus. Embryo splitting c used in animal husbandry to produce more specimens is something Urur uos reckons has a particularly good inheritance material. Occasionally, embryos also happen to result in individuals being genetically identical. of an animal splitting naturally, such as when we have single twins. embryo Splitting. In animal breeding, cloning may be appropriate. Especially valuable bulls and horses, for example, have been cloned. Discussions have now begun on whether cloned cows and oxen (or their offspring) can be sent to the slaughterhouses in the usual way and eaten by humans. Should meat from these animals be labeled with the aclon »? In the United States, the authorities have decided that meat from cloned animals is similar to meat from non-cloned animals, and that such meat can be sold without special labeling. Similarly, horse environments discuss how to deal with cloned horses. For example, should two clones be able to stand in the same race? Both cats and dogs have been cloned, and those behind the clone wanted to make money cloning people's pets.

Inheritance, environment and epigenetic inheritance

There is a continuous discussion about how we as individuals are both physically and mentally affected by inheritance and the environment. In some cases, certain traits have almost exclusively genetic causes, other times we find the causes almost only in the environment, but in most cases there is an interaction. Very often we have a genetic predisposition, and then it can be read by an environmental impact. We have just looked at some of these types of environmental pathogens, but it has also been shown that epigenetic changes, ie changes in the genome without changes in the nucleotide sequence, can significantly affect the expression of genes. Such changes can often be driven by environmental impacts. In the last ten years, there has been a great deal of research on epigenetic changes that can act as switches on and off genes. In the section on gene regulation in chapter 5 you read about how this is done. More and more, it has been discovered that environmental influences, both physical and psychological, can have such epigenetic effects on both physical and mental properties. This is why single twins that grow up in the same environment remain fairly similar, while single twins with different upbringing environments can develop significantly larger differences throughout life. This is because different growth environments mean that it is not the same genes that are activated and deactivated in each of the twins. But it shows that for an individual's life cycle, the environment can be more important than previously thought. Epigenetic changes are less stable than changes in the nucleotide sequence. They are most often eradicated when the germ cells are formed. We can say that the germ cells are reprogrammed and are able to express all the genes necessary to develop an organism. But recent research suggests that some epigenetic changes can be preserved in the germ cells and inherited to the next generation.

Cloning of DNA in the bacterium E.coli

What is a clone? Bacteria propagate unfamiliarly by two-partition, and strawberry plants form offspring that give rise to new strawberry plants, examples of natural cloning "Children are genetically identical to their" parents. A clone is therefore a genetic copy, and cloning can be defined to produce genetically identical copies of DNA molecules, or of whole individuals. Here we will look more closely at the cloning of DNA molecules. Later in the chapter we come back to ay cells cloning of cells and whole individuals. Because genes are small pieces of DNA, we must make many copies of a gene to be able to examine it, modify it, splic it with other genes or insert it into other organisms, We make it by making clones which can mass-produce DNA bits can be cloned by transferring the gene to a living cell. can also be done chemically, without the use of cells, using PCD It is common to use PCR for cloning when the sequence of the desired genes is known. The intestinal bacterium Escherichia coli (E.coli) is among other things in the colon. but with us humans and is one of the most studied organisms found. This bacterium is widely used for cloning DNA. E.coli has one plasmid, but it can also accept artificially produced plasmids specially made for cloning. These plasmids often contain genes for antibiotic resistance, so-called marker genes. They show whether the bacterium has taken up the plasmid. Plasmids with marker genes can be opened with restriction enzymes. The desired gene can then be pasted into the open plasmid by a ligase enzyme. Plasmids that now have both the marker gene and the desired gene can then be inserted into E.coli, which then becomes a genetically modified organism (GMO). For that we can, for example, use high electrical that makes the cell membrane holes and make the cell susceptible to DNA. voltage The bacterial cells are then cultured on a nutrient medium, a gel, to which antibiotics are added. Only bacterial cells that have taken up the plasmid that has the marker gene for antibiotic resistance will then survive and multiply. Bacterial cells that survive will be those that also contain the desired gene and can then be grown in large quantities. All cells now contain the same desired and inserted gene. When a gene is cloned into a living cell, it can often be expressed by producing the protein that the desired gene encodes. In research, this is often used to study the function of genes and how they can be regulated. The industry uses this technique to mass produce proteins, e.g. for medical use.

Genetically modified animals

When plants are to be genetically modified, it is common to start with different specialized cell types. When we are going to make animals that are genetically modified in all their cells, it is not usual today to start that way. It is only when we change the inheritance in a fertilized egg cell (zygote) that the changes will surely be passed on to the next generation. Shortly after conception, a zygote contains two haploid nuclei with each parent's chromosome set. One nucleus was in the egg before fertilization, the other came with the sperm. After a few hours, the two nuclei will melt a diploid core. Foreign or altered DNA can be inserted by microinjection. That is, the foreign DNA is injected into the zygote using very thin glass tubes, capillary tubes. When we insert DNA into one haploid nucleus, the chance of the DNA becoming part of one or more of the chromosomes in the cell increases. The zygote is then inserted into a surrogate mother for normal fetal development. The inserted DNA is copied with the chromosomes before cell division. If the inserted DNA has become part of the chromosomes in the cell, all cells that develop in the animal will contain the inserted DNA. In order for a modified gene to give rise to a new phenotype, it must be dominant to the normal allele, which is still present. This method is very demanding - both because the DNA supply itself is very common, and because many of the zygotes die. Only between 1 and 30% of the 2,88 with DNA added yield genetically modified animals. The alternative is to insert ge into embryonic stem cells. Embryonic stem cells we come to on page 246. In most cells that take up foreign DNA, the foreign DNA is inserted randomly into the chromosomes of the cell. In the worst case, this can cause vital genes to be destroyed and the animal to die. To some extent, the debut is to control where the inserted DNA is to be inserted. A mutated gene can thus be replaced with a gene that works, or a functioning gene can be replaced with a broken (mutated) gene. By studying changes in animals where both the alleles of a gene are destroyed, scientists can find out more about the function of the healthy gene. Studies of animals with mutated genes can further make it possible to develop therapies for diseases.

The active site

When we draw a model of an enzyme, we simplify the chemical structure, the formula and draw something that looks almost like a lump, the lump consists of both the protein part of the enzyme and the cofactor. The model of the enzyme shows a very simplified shape. It must have "empty spaces - for each of the substrates These empty spaces symbolize the binding site where the substrates can react and form product (s). The active site we call this binding site. Only some specific substances - the substrates - can "settle into the active site. The active site has room for one or more substrates that are part of a chemical reaction, and we say that the reactions are enzyme-specific. When we explain this term, we often talk about "key-in-lock". Just as only one particular key can unlock one particular mandrel, there is one particular enzyme that is specialized to participate in one particular reaction. When a chemical reaction is to take place using enzymes, the substrate molecules attach themselves briefly to the active site. The purpose of this is to allow the substrate molecules to "sit next to each other" for a short while. Then they come so close together that a chemical reaction can occur between them. The placement of the substrates in the active site causes the activation energy to be lowered and the reaction proceeds faster. After the substrates have reacted and formed a product, the product releases from the active site. It is this mechanism that makes the enzyme a catalyst. The enzyme affects the reaction, but it is not used up. It can be used again and again. Thus, the cell does not need to spend as much resources on creating new enzymes. The figure shows how two substrate molecules become a refrigerator. Enzymes also participate in reactions in which a substrate is converted into several product products.

Gel Electrophoresis

When we work with DNA techniques, we cannot see the DNA directly. Instead, we must use a large number of copies of the gene or DNA bit we want to examine. By using dyes that bind to DNA, we can then make visible the molecules of DNA. An example of such a dye is ethidium bromide (EtBr), which binds between the base pairs and fluoresces by UV illumination. Gel electrophoresis is used to separate DNA fragments of different sizes. Until a gel is used, ie a gel-like medium. The gel is placed in a vessel with a live solution containing ions. When we turn on electricity, the gel gets a positive and a negative side (pole). Because DNA molecules have a negative charge, they will move towards the positive pole when exposed to electrical current. The gel is full of small pores that allow small molecules to pass through it easily, while large molecules face more resistance and migrate more slowly. When the DNA pieces are sufficiently separated in size, the electrophoresis is complete and the DNA is faneos with, for example, EtBr. We can find the size of the DNA bits by comparison with a DNA standard, where there are DNA bits of known starches. The DNA bit you want to study further, can be cut out of the gel and purified, and then used for example to cloning, for genetic fingerprints, sequencing, etc. One form of gel electrophoresis is capillary electrophoresis. Instead of a large gel, thin tubes (capillary mother) smaller than 0.1 mm in diameter are most often used. Here, too, the DNA is separated by size. The result of the gel electrophoresis is read automatically by a computer. Gel electrophoresis and capillary electrophoresis are used in DNA sequencing and to prepare genetic fingerprints.

Pyruvic acid to lactic acid

When you exercise hard, you need a lot of energy quickly. The breakdown of large carbohydrate molecules gives glucose, and further breakdown of glucose gives you energy. As you exercise, you breathe extra deep and expand your lung volume so you get a lot of oxygen into your lungs. Nevertheless, you may not get enough oxygen for just aerobic cell respiration, and the muscle cells must then switch to anaerobic glucose degradation. Humans and other mammals also have enzymes to be able to have anaerobic degradation when access to oxygen is too small to operate aerobically. Then pyruvic acid becomes lactic acid. Our anaerobic degradation to lactic acid is reversible. The reaction can thus go back. When we rest and breathe in enough oxygen, lactic acid is converted into pyruvic acid that enters the crayfish cycle and on to oxidative phosphorylation. Lactic acid accumulation in the muscles makes you stiff. The tolerance for lactic acid in the muscles varies from person to person. We can train ourselves to endure more. A stiffening during a skiing literally means that the muscles cannot be stretched or contracted because they are not getting enough ATP. Moving slightly and stretching well after exercise will allow you to transport oxygen-rich blood to your muscles more easily and lactic acid will be converted. Some parts of our body just have anaerobic breakdown. The cells in parts of our eye, for example, the cells on the back of the cornea, do not need as much energy, and they do not supply much oxygen through blood vessels, so they cope with the energy they get from anaerobic glucose degradation. to lactic acid. The rest of the body must have aerobic glucose degradation to get enough energy for movement, diaphragm transport and chemical work. When we make milk products such as beverage yoghurt and sour cream, we usually use sweet milk and add lactic acid bacteria, e.g. Lactobacillus. In the glycolysis and anaerobic degradation of pyruvic acid, Lactobacillus uses the same enzymes as we do. First, the bacteria convert the milk sugar to glucose, then they convert the glucose to pyruvic acid and then to lactic acid. Lactic acid from Lactobacillus causes the milk proteins to be denatured, that is, the milk separates or thickens. We can take out the cheese for cheese and yogurt production. In anaerobic decomposition to lactic acid, no carbon dioxide is formed: and using it 1 glucose + 2 P + 2 ADP 2 lactic acid + 2 ATP + 2 water The energy yield per glucose molecule is only 2 ATP against 32 in the aerobic decomposition. The two molecules of NADH that were formed in the glycolysis are used when pyruvic acid becomes lactic acid, and we get NAD again.

Enzymes in the reaction pathway are regulated

With hundreds of reactions, substrates, enzymes and products in tissue cells, it is easy to think that complete chaos can easily arise here. However, it did not happen. The reason is that the reaction pathway is regulated so that it can act back on the first enzyme in the reaction pathway. Then it becomes real. the end product made more end product than needed, or it is made more ay sluggish product because it is needed. A large amount of the final product causes the enzyme to be inhibited, inhibited, while a small amount of the final product causes the enzyme to be stimulated, activated. Also, the amount of substrate kin in some cases affect and inhibit or activate the enzyme. The amount of the end product C in the figure on the previous page affects the activity of the first enzyme upon feedback. C may be inhibitory so that the reaction stops as in b, or C may act as a stimulus to increase the reaction rate as in c. If C is inhibitory, we call it negative feedback or negative feedback. If C is stimulating, we use the term positive feedback or positive feedback.

From pyruvic acid to ethanol or acetic acid

Yeast fungus can have both aerobic and anaerobic degradation. By anaerobic degradation, pyruvic acid is converted to the alcohol ethanol and carbon dioxide. Examples of such yeast fungi are olive yeast. Bread yeast and olive yeast break down the starch in the grain of glucose, Vinpyruvic acid. Bread yeast, wing yeast and yeast break down sucrose and fructose into the fruit of glucose. When we make a bread dough, we use liquid with a temperature now about 37 C, because then the fungal cells divide the fastest and operate with anaerobic respiration. The carbon dioxide they produce raises the bread dough. Getting the dough smells like alcohol. When the dough is fried, the alcohol evaporates. The energy from glycolysis goes to heat; the temperature of the dough rises. The breakdown is as follows: lots of 1 glucose + 2 P + 2 ADP + 2 H → ethanol + 2 carbon dioxide + 2 ATP + 1 water Also yeast uses up the two NADH from the glycolysis when it produces ethanol, so that the net amount of energy from one glucose molecule is 2 ATP. All yeast cells contain the specific enzymes needed to form ethanol. Ethanol formation is irreversible; ethanol cannot, therefore, return to pyruvic acid. The yeast cells die when the amount of alcohol in the bread dough, wine or beer is approx. 15%, Acetic Bacteria contains enzymes that can break down pyruvic acid into acetic acid. This happens anaerobically. Acetic acid bacteria can also convert ethanol into an alcohol-low solution such as wine or beer into acetic acid. However, this reaction occurs aerobically. Acetic bacteria are normally found in the kitchen. Such bacteria that come into contact with beer or wine which is open and with access to oxygen will convert the ethanol into the oil or wine into sour vinegar. We make use of this reaction in the industry when we produce wine vinegar. The acetic bacteria can withstand very low pH and are not killed during production.

Enzymes can produce a faster reaction that requires less energy

You have just read that the enzymes act as biological catalysts because the reactions require less activation energy and therefore can go faster. We will look at two examples of enzymes: carboxylic acid anhydrase and catalase. Carbonic anhydrase is a very effective enzyme found in all living organisms. It helps to remove carbon dioxide gas produced in the body by aerobic cell respiration. The carbon dioxide gas must be removed quickly to prevent the blood from reaching too low a pH, thus becoming too acidic. This enzyme catalyzes the reaction in which the gas carbon dioxide reacts with water to carbonic acid and further to hydrogen carbonate and hydrogen ions: CO, + H, 0 - H, Co, - HCO, + H In this reaction, it is with substances that act as a buffer, The pH of the blood is counteracted. This is important, because most reactions in the body can only occur at a pH of around 7.4. A change in pH of more than 0.4 can be life-threatening. The blood therefore contains buffers that counteract pH changes. Hydrogen carbonate is formed which is soluble in the body fluids and is transported with the blood to the gas exchange organs, where the opposite reaction occurs: HCO, + H → H, CO, - CO, + H, O The carbon dioxide gas is thus removed from the blood, and The pH increases again. Also in this reaction, the enzyme participates carbonic anhydrase. Carbon dioxide exits the blood vessels and into the lungs by diffusion because the concentration of CO, is lower in the lungs than in the blood. One enzyme molecule of carbonic anhydrase causes 100,000 molecules of carbon dioxide to react per second. The reaction goes 10 million times faster than without enzyme. The enzyme catalase is important for breaking down hydrogen peroxide, H, O,. In the cells of all living organisms, hydrogen peroxide is formed as a by-product of metabolism (metabolism). Hydrogen peroxide is toxic and very reactive and must be broken down immediately. Therefore, all living organisms have the enzyme catalase. It splits hydrogen peroxide into water and oxygen gas: * O + O'H-'O'H Without enzyme, an activation energy of 75 kJ / mol is needed. When catalase is present, an activation energy of only 8 kJ / mol is enough. Catalase lowers the activation energy by about 90% compared to the activation energy without enzyme, and the reaction goes much faster. The curve below shows the difference in the required activation energy with and without enzyme in an exothermic reaction. When the activation energy goes down because enzyme is present, the reaction rate increases.

Glycolysis: glucose degradation

glucose (hexagonal carbon, 6C) is the first compound in the main part v called glycolysis. Glucose is a monosaccharide. It is formed in photosynthesis and when larger carbohydrates such as glycogen, starch or sucrose are cleaved. All living organisms share the biochemical degradation of glucose. The glycolysis takes place in the same way either the aerobic or anaerobic. We find it in all cells of all living organisms, in the cytosol, the cell fluid. The degradation in glycolysis occurs through eleven partial reactions. For each reaction, specific enzymes are needed. Here we only include the main features. When ATP releases a phosphate group to another molecule, the other molecule increases its chemical energy. Two ATP molecules are cleaved and the two energy-rich phosphate groups (P) are transferred to a glucose molecule. We get an unstable energy-rich molecule of fructose 1,6-biphosphate (6C). Fructose 1,6-biphosphate is rapidly cleaved into two molecules of triose phosphate (wood carbon, 3C). In the next partial reaction, triose phosphate is converted, and the phosphate groups and energy are transported. Some of the energy is then used in reactions where four electrons and two H ions are bound to form two molecules of energy-rich NADH. At the same time, four ADPs, 4 P (two P from the triose phosphates and two free P), are bound together to give us four ATPs. The two charcoal compounds that are formed after phosphate groups are removed are two molecules of pyruvic acid (3C). Thus, one molecule of glucose (6C) was split into two molecules of pyruvic acid (3C) at the same time as energy was transferred to two different energy-carrying molecules, ATP and NADH. The energy sources that are formed by the breakdown of one glucose molecule in the glycolysis are 4 ATP (formed) - 2 ATP (used) = 2 ATP 2 NADH. The breakdown of glucose into pyruvic acid is regulated by ATP, which thus also acts as an enzyme inhibitor (inhibitor). Much ATP inhibits the enzymes that will act in glycolysis, and glycolysis stops for a certain time. When the amount of ATP decreases, glycolysis starts up again.

Inhibitors affect enzyme activity

inhibitors, can affect enzymes in two different ways: an irreversible (cannot be sniffed) and a reversible measure (can be sniffed). In the event of an irreversible inhibition, the structure of the enzyme is destroyed and cannot be restored (see the figure below). Three examples of irreversible inhibitors: pesticides sprayed on food plants to kill insects, cyanide used in poisonings, nerve gas used in biological warfare. A little about nerve gas: It affects the nerve cells' production of the transmitter acetylcholine and the enzyme acetylcholine esterase. It is this enzyme that breaks down acetylcholine. The nerve gas thus leads to paralysis. We divide reversible inhibitors into competing and non-competing. The competing inhibitors can block the active site so that the substrate cannot adhere (see the figure on the next page). But the inhibitors can loosen so that some substrate molecules can adhere if we increase the substrate volume sharply. An example of competing inhibitors is methanol and ethanol. Methanol poisoning can be cured by allowing the patient to receive large amounts of ethanol. In the body, methanol and ethanol are broken down by the same enzyme. They compete for space in the active seat. By decomposition of methanol formic acid is formed. Formic acid leads to acid poisoning (acidosis). It destroys the blood vessels and leads to the complete or partial blindness of those who survive. At worst, the result can be death. The death is due to the end-organs being paralyzed by formic acid. A person who has been drinking methanol can get ethanol because ethanol adheres more easily to the active site in the enzyme than methanol, and this enzyme essentially breaks down the ethanol. The methanol is then excreted directly without being broken down and in minor damage to the body. The non-competitive inhibitors do not bind in the active sites but elsewhere on the enzyme, in the so-called allosteric sites. Then the enzyme changes shape and it becomes less active because the substrate may have difficulty. lighter to attach to the active seat. An example: During cell respiration, a great deal of ATP is produced, and ATP acts on the cell respiration enzymes by attaching ATP to allosteric sites of several of these enzymes, the OE cell respiration then slowing down.

tRNA and ribosomes

tRNA carries amino acids from the cell's storage to the ribosomes where the proteins are made. Also, the tRNA is transcribed from specific genes in the cell nucleus and migrates to the cytoplasm where translation occurs. Each tRNA consists of an RNA strand and is approx. 80 nucleotides long. The tRNA strand is folded into a three-dimensional structure with the shape of an inverted L. At one end of this L-formation there is a triplet. This triplet can bind to one specific mRNA codon. The triplet in the tRNA is complementary to a codon on mRNA and is therefore called an anticodon. The other end of the L is the attachment point of an amino acid. Each tRNA picks up and delivers only one specific amino acid and is utilized several times. Of the 64 different codons, there are 3 codons that have no complementary tRNA, and it is the three codons that act as a stop signal. 45 different tRNAs recognize the remaining 61 different codons and deliver the 20 amino acids needed to build whole proteins. Thus, some tRNA may recognize several codons. This is possible because the third base in codon and anticodon does not always need to pair correctly. When U is the third base of an anticodon, it can pair with both A and G. In order for a Gaussian message to be accurately translated, there must be a correct match between the tRNA and the amino acid to pick it up. With the help of 20 different enzymes, one for each amino acid, the right amino acid is attached to the right tRNA. Proper translation also requires hits between mRNA codon and tRNA anti-codon. Thus, tRNA acts as an interpreter because it can read the genetic "orders" of the mRNA codons and translate them into amino acid "words". It is the ribosomes that provide the link between mRNA codon and tRNA antibody. A ribosome is made up of a large and a small part. Each part is composed of proteins and rRNA. FRNA makes up two-thirds of the mass of ribosomes. Because most cells contain several thousand ribosomes, FRNA is the most common type of RNA. Each ribosome has a site where mRNA can bind. In addition, the ribosome has three sites where tRNA can bind: One site holds the empty tRNA that has delivered its amino acid to the polypeptide chain. The center site is used to hold the RNA carrying the growing polypeptide chain, and the last site holds the RNA that delivers the next amino acid to be bound to the polypeptide chain. The ribosome provides for the formation of peptide bonds between the amino acids in the polypeptide chain. The growing polypeptide chain is directed through an opening in the major portion of the ribosome and released into the cytoplasm when the polypeptide is complete.

Use of mitochondrial DNA to identify

to be able to compare the repeated DNA sequences between the genes must have DNA from the cell nucleus. While the core DNA can be broken down into ancient biological material, mitochondrial DNA is more protected and can be intact. In each cell there is a much higher number of copies of mitochondrial DNA (hundreds of copies of each mitochondrial chromosome) than of nuclear DNA (only two copies of each chromosome). The use of mitochondrial DNA can therefore be useful as evidence in old unresolved criminal cases. Because mitochondria are only inherited from the mother, all close descendants of a mother will have identical mitochondrial DNA. This makes mitochondrial DNA less suitable to distinguish between relatives. Mitochondrial DNA mutates at relatively fast and stable speed, therefore it is well suited to differentiate between unrelated individuals. By analyzing mitochondrial DNA from a broad range of Earth's population groups today and comparing the results, it has been possible to calculate when a theoretical ancestor must have lived. By tribal mother we mean the individual from which all living people are descended. The theory says that this must have been a woman who lived in Ethiopia, Tanzania or Kenya 140,000 years ago. She has been called the mitochondrial Eve. The same DNA technique used in forensic medicine is used to study. you populations of other animals and relationships between individuals. Among other things, genetic fingerprints have been used as evidence when it comes to environmental crime. In connection with the Scandinavian wolf project Skandulv, a register was created with genetic fingerprints from all wolves that were radiolabelled in Sweden and Norway, as well as prints from a number of wolves from which stools or urine with blood have been found. In this way, it is possible to link tissue samples to specific wolf individuals who have been killed illegally. The technique has also been used in a national program for monitoring large predators. Through the collection of excrement from bears we have been able to analyze genetic fingerprints in the Norwegian bear strain. In the faeces of bears, there are intestinal cells that have enough intact DNA to be analyzed and used to identify species, sex and individual and also disease with other bears. By examining a large number of excrements, the researchers have in this way gained knowledge about individuals' migration patterns and an overview of how large the population of Norway is.