Bio Exam 3

What is the blended hypothesis?

(This is an old idea that is not correct, but we cover this from a historical standpoint.) The blending hypothesis offers an explanation of how parents with contrasting appearance always produced offspring of intermediate appearance. While this basic premise is true, the traits of the parents with contrasting appearance do not blend together to achieve the intermediate trait. The example that was often used to explain this is that when certain red flowers are crossed with white flowers, the offspring are pink. Red flower x White flower ----> Pink flowers However, in later generations when a pink flower was crossed with another pink flower, the offspring that resulted were 25% red, 25% white, and 50% pink. How could the intermediate pink color come unblended? This makes no sense if blending was really how things worked. What is really going on here is incomplete dominance.

Given a particular genotype, be able to figure out the different kinds of gametes (combinations of alleles) that could be formed.

(You can use the "FOIL" method to form the combinations of alleles in the gametes.) Let's use the following genotype as our example: AaBbI will rewrite this genotype as (Aa)(Bb). "FOIL" represents the following: F stands for "first" times "first." That is, the first A combined with the first B giving an AB combination. O stands for "outside" times "outside." That is, the outside A combined with the outside b giving an Ab combination. I stands for "inside" times "inside." That is, the inside a combined with the inside B giving an aB combination. L stands for "last" times "last." That is, the last a combined with the last b giving an ab combination. There are four possible gamete combinations: AB, Ab, aB, and ab.

What is Mendel's Rule/Law of Segregation?

1) Each organism contains two factors (genes) for each trait. These two factors separate during the formation of gametes so that each gamete contains only one factor (gene) for each trait. 2) Upon fertilization, the new organism will have two factors (genes) for each trait, one from each parent

Dominant allele

= allele that masks the expression of another allele. * one that shows up Dominant can refer to the genes or to the traits they control. Dominance is determined by observing the trait (characteristic) in the heterozygous condition. Dominant does NOT mean that the trait is better, more abundant, or that it will increase in the population over time. Only one copy of a dominant allele is required in order to show a dominant trait. We will use a capital letter to represent a dominant allele.

Define dihybrid cross.

A dihybrid cross is a genetic cross that involves two different traits/characteristics. ex: freckles and dimples

What is a karyotype? What kind of information can be learned from examining a karyotype?

A karyotype is an arrangement of the chromosomes of an individual. The chromosomes are arranged from the largest homologous pair to the smallest homologous pair. The sex chromosomes are the 23rd pair. You will see that for each karyotype, the first 22 blanks show the autosomes and the 23rd blank shows the sex chromosomes. The karyotype on the top has two X chromosomes and would be that of a female. The karyotype on the bottom has one X andone Y chromosome and would be a male. If you look at space 21 on this second karyotype, you'll notice that there are three copies of chromosome 21. This male will also have Down syndrome (Trisomy 21).

What is a linkage group? How are crossing over and recombination influenced by the distance between two genes on the same chromosome?

A linkage group refers to all the genes located on a particular chromosome. This means that those genes are "linked" to that chromosome (like my passenger on the bus analogy). It turns out that the closer that two genes are on a chromosome, the more tightly they are linked. The genes will travel together as a package deal and will not be separated as often by crossing over or recombination. Have you ever noticed how red hair and freckles seem to show up together? The genes for red hair and for freckles probably travel close together on the same chromosome and don't get split up by crossing over very often. Genes that are far apart on the same chromosome are routinely shuffled by crossing over.

Define monohybrid cross.

A monohybrid cross is a cross involving only one trait.

What is a mutation?

A mutation is a permanent change in the DNA of a gene or a chromosome. Mutations can only be passed on to offspring if the mutation is present in the gametes (eggs or sperm). The instructions in the gametes are the only thing you pass on to your offspring (genetically speaking).Also, mutations happen randomly. We cannot predict when, where, or how DNA might mutate. It just happens. Mutations don't occur for a reason.

What is a reciprocal cross?

A reciprocal cross really involves two separate crosses. A reciprocal cross is performed to determine if the pattern of inheritance is independent of the parents' sex. For example: Cross #1: pollen (male) from tall pea plant X egg (female) from dwarf pea plant yields all tall pea plants Cross #2: pollen (male) from dwarf pea plant X egg (female) from tall pea plant yields all tall pea plants In other words, the offspring will all be tall and it doesn't matter which parent was the tall one and which was the dwarf. Most of the time sex does not matter, but sometimes it does (ex: Huntington's Disease)

What is a testcross? For what purpose is it used?

A testcross is a cross in which one individual with a dominant phenotype is crossed to an individual with a recessive phenotype. By looking at the offspring produced, one can then determine if the individual with the dominant phenotype is homozygous dominant or heterozygous. This technique is used in breeding experiments in order to determine if an individual with a dominant phenotype is pure-breeding or not. If any offspring from a testcross show the recessive trait, then the dominant phenotype individual must be heterozygous. General Rule: In a monohybrid testcross, if a 1:1 phenotypic ratio appears, then the dominant phenotype parent must be heterozygous.

Compare asexual reproduction with sexual reproduction.

Asexual reproduction: reproduction by binary fission or mitosis. Only one organism/cell involved that divides into two. Daughter cells are identical. (w/o sex) Sexual reproduction: reproduction through the fusion of male and female gametes/sex cells. Gametes are produced during meiosis. Two organisms (male and female) are involved. The offspring produced via sexual reproduction are genetically different than either of the parents. This allows for genetic diversity (different combinations of genes) among the offspring.

Give examples of disorders that exhibit autosomal dominant inheritance.

Autosomal dominant disorders occur if the individual inherits one or two copies of the dominant allele. Because these are dominant alleles, only one needs to be present to express the trait. Most people who have these disorders are heterozygous. (You would have to be pretty darned unlucky to get a dominant allele from each of your parents.) Here are two examples of autosomal dominant disorders: a) Neurofibromatosis (NF)This is also known as the elephant man disease. One out of 3,000 people suffer from this disorder, so it is fairly common. This disease occurs in every race and ethnic group. Tannish colored spots develop on the skin (café-au-lait spots) that increase in size and number. This is where nerve cells are proliferating and become benign tumors called neurofibromas. These occur under the skin, in the muscles, and in the central nervous system. This eventually causes learning disabilities, skeletal deformities such as large head, eye and ear deformities that lead to blindness and hearing loss. b) Huntington disease (HD) One out of 20,000 people suffer with this disease. It is a common inherited brain disorder that involves degeneration of brain cells. It doesn't show up until middle age (when people have already had children and passed the genes on to their offspring). Symptoms include involuntary jerky movements, twitching movements of facial muscles, slurred speech, difficult swallowing, loss of balance, mood swings that can be severe at times, impaired reasoning and memory problems. Death results from pneumonia or heart failure. There is a genetic test for this so people can find out if they have the dominant gene. This may be of particular interest if others in their family have had this disorder.

Give examples of disorders that exhibit autosomal recessive inheritance.

Autosomal recessive disorders occur if the individual inherits two copies of the recessive allele (that is, they are double recessive). Each parent must be a heterozygous carrier of the recessive allele and pass the recessive allele to their offspring. Examples include: a) Cystic fibrosis This is the most common lethal genetic disease among Caucasians. One in 25 Caucasians is a carrier for the cystic fibrosis allele. This disorder causes a thick mucus to build up in the lungs and the individual has difficulty breathing. They also have some digestive problems. It used to be that those with cystic fibrosis died in their teens. Now with new drug therapy and vibrating vests that can shake loose the mucus deposits to help them cough the deposits up, they can live into their early 30s. There is no cure for cystic fibrosis .b) Tay-Sachs disease This is a genetic disease seen among those of Jewish descent. There is no cure. When a baby is born with two recessive copies of the Tay-Sachs allele, development is normal until about 4-8 months of age. Development slows down at that point because the myelin sheath that insulates the nerves starts to build up too thick. This impedes the flow of nerve impulses. The baby starts to have nerve and motor/movement difficulties. Blindness develops. They lose their hearing and sense of touch. They have seizures and become paralyzed. The child dies by age 3 or 4. c) PKU (phenylketonuria) This is a common enough disorder that all babies are checked for it in the hospital. All that is needed is a drop or two of blood to check for the presence or absence of an enzyme that can break down the amino acid phenylalanine. For those babies who do not have the enzyme, their parents are given strict instructions on a rigid diet that must be followed to prevent the toxic buildup of phenylalanine. They must avoid all foods with high levels of phenylalanine including anything that has the artificial sweetener aspartame (Equal and NutraSweet in the blue packets), red meat, and other foods on the list. If too much phenylalanine builds up that cannot be broken down and metabolized, then it retards brain development. The brain may only develop to a mental age of two years old! Once persons with PKU reach puberty, a time when brain development is assumed to be nearly complete, they can introduce some foods containing phenylalanine into their diets. It won't regress the brain development achieved thus far. However, it probably wouldn't be wise to eat steak and eggs for breakfast, a huge hamburger for lunch, and roast beef for dinner washing it all down with diet soda. Females with PKU who become pregnant are advised to go back on the PKU diet so as not to potentially harm the developing fetus.

What are autosomes? How many pairs of autosomes do humans have?

Autosomes are any chromosomes that are NOT sex chromosomes. Humans have 22 pairs of autosomes. When you see traits described as being autosomal, that means the genes are on one of these 22 pairs of chromosomes.

benign tumors vs malignant tumors

Benign Tumors noncancerous cells remain differentiated encapsulated uniform shape do not spread/metastasize not life-threatening Malignant Tumors * mal=bad cancerous cells are undifferentiated not encapsulated not uniform in shape, can have "feelers" can, and often do, spread/ metastasize life-threatening

What kind of cell division occurs in prokaryotes?

Binary fission = the type of cell division in prokaryotes 1) The chromosome replicates 2) The chromosomes separate as the cell elongates 3) The cell divides into approximately two equal portions

Phenotype

Characteristics that are expressed, but not necessarily seen. Phenotypes may be morphological (physical), physiological (chemical), and/or behavioral. The phenotype may change continually throughout the life of the organism. ex: greying of hair with age (We use word descriptions for phenotypes.) Examples would be: tall, short, freckled, Widow's peak, blue-eyed, brownhaired, etc.

What is codominance? Give an example.

Codominance is a pattern of inheritance in which the heterozygote shows BOTH traits to their FULL EXTENT. You do these problems just like the incomplete dominance problems I have described above. the heterozygote in this case doesn't show an intermediate trait, it shows both traits at either end of the spectrum together at the same time. Example: Roan coat color in cattle C1 = Red hair allele and C2 = White hair allele The possible genotypes and corresponding phenotypes would be as follows: C1C1 = Red hair C1C2 = Roan (combination of red hairs and white hairs) C2C2 = White hair Note that the heterozygote will have red hairs just as red as on the red cow and white hairs just as white as on the white cow. Both the red and the white hairs show up to their full extent. The color isn't faded out or anything like that. Now, there is another example of codominance you need to know and that is the AB blood type in humans. People who have AB blood show both the A markers and the B markers on the membrane surface of their red blood cells.

What causes a cell to continue to divide or prevents it from doing so? How is cancer related to mitosis?

Control Cycle of the Cell: 1) Outside influences such as hormones or growth factors 2) Adhesion to a Solid Surface - The cytoskeleton of cells has to have a solid surface to push against in order to divide. 3) Contact Inhibition - Normally, when neighboring cells touch each other, they stop dividing. Mitosis is related to cancer. Cancer is uncontrolled cell division. Cancer cells do not grow and divide faster than normal cells. The problem is that they do not stop growing, dividing, or moving on contact. Cancer cells crawl over other cells, invade healthy tissues, and multiply into masses called tumors ( cancer cells ignore #3) Metastasis = the spread of cancer cells from their site of origin to other parts of the body. "beyond control"

What is crossing over? What is its significance?

Crossing over occurs during meiosis I when the homologous pairs are side-by-side. The maternal and paternal homologs exchange material (genes) with each other. Usually, it is an equal exchange (but not always). The significance of crossing over is that it enhances genetic diversity. This is how genes get "shuffled" between homologs so that the gametes produced contain chromosomes with a combination of genes from the maternal and paternal parents.

Define cytokinesis. How does cytokinesis differ between plant cells and animal cells?

Cytokinesis = division of the cytoplasm and its contents In plant cells, a cell plate forms to divide the parent cell into two daughter cells. (See diagram included in your files.) In animal cells, the cell invaginates all the way around and pinches itself into two daughter cells. (See diagram included in your files.)

What is the relationship between DNA, chromatin, and chromosomes? What is a chromatid? What is a centromere?

DNA = the genetic material (deoxyribonucleic acid) Chromatin = a loosely arranged form of DNA seen when a cell is not actively dividing Chromosome = a tightly condensed form of DNA seen when a cell is actively dividing. (One chromosome = one molecule of DNA) - 46 chromosomes in each human cell Chromatid = one half of a duplicated chromosome Centromere = constricted region made of DNA that holds two sister chromatids together before they separate; Also, the indented or constricted region on a chromosome; sometimes the centromere is located toward the middle of the chromosome, sometimes it is off center, and sometimes it is more toward the end. * humans don't have any on the end The location of the centromere is one way that chromosomes can be identified.

Define diploid and haploid

Diploid = 2N where N represents one complete set of chromosomes; "Chromosomes, and the genes they carry, come in pairs just like Levis come in pairs." All body (somatic) cells are diploid with the exception of sex cells (eggs and sperm). Haploid = N There is only one complete set of chromosomes in a haploid cell. The only haploid cells in animals are the sex cells (eggs and sperm). N= 1 complete set of chromosomes Humans= 23

What causes Down syndrome?

Down syndrome is usually (96% of the time) caused by having three copies of chromosome 21. (About 4% of the time, it is caused by a Robertsonian translocation where the long arm of chromosome 21 attaches to chromosome 14. The person ends up with two full copies of chromosome 21 and about three-quarters of another chromosome 21. This is enough to show the symptoms of Down syndrome. This is usually the type of Down syndrome that can run in families. If you see parents with more than one child with this condition, it might be that they have this Robertsonian translocation.)The typical symptoms of Down syndrome are: - some degree of mental deficiency (Some individuals are high functioning, but others are not.)- a distinctive palm print called the Simian crease where there is one main crease across the palm of the hand- extra folds of skin on the eyelids- wide set eyes- enlarged tongue- heart problems (Many pass away in their 50s or early 60s because of heart issues.)

Be able to do some monohybrid cross genetics problems. (See examples done in class and the practice problems provided in the text.)

First of all, we must know which trait is dominant. E = unattached earlobes (the dominant trait) e = attached earlobes (the recessive trait) Problem A: Suppose a man homozygous for unattached earlobes reproduces with a woman who has attached earlobes. What types of earlobes, and in what proportion, will their children have? genotipic ratio: 100% phenotipic ratio: 100% unatattched Problem B: Suppose two individuals who are both heterozygous for unattached earlobes reproduce. What types of earlobes, and in what proportion, will their children have? genotypic ratio: 1EE: 2Ee :1ee phenotipic ratio: 3 unattached: 1 attached

Define: gamete, homologous chromosomes.

Gametes = sex cells = eggs and sperm. Homologous chromosomes = pairs of chromosomes that carry genes for the same traits although the expression of the traits may be different for each. One homolog comes from the mother and the other homolog comes from the father. (23 pairs in human) ex: brown eyes from mom, green from dad

What is the relationship between chromosomes and genes?

Genes are located on chromosomes. Depending on the size of the chromosome, it may carry hundreds or thousands of genes. Think of the chromosome as a bus and the genes as the passengers on the bus seated one after another after another. The "seat" or place/address where the gene is located on a chromosome is called its locus. (Locus sounds like location.) Chromosomes segregate (separate) during meiosis; and therefore, so do the genes they carry. (Wherever the "bus" goes, so do the "passengers.")

Genes code for what kinds of products?

Genes/alleles code for proteins, enzymes, and hormones. (Enzymes and hormones are types of proteins too.)

How do you tell a genotype from a gamete when they are written in symbolic (letter) terms?

Genotypes are diploid. (Genes come in pairs.) Examples: Aa, AA, AaBb, ccDdEe, XxYyZz Gametes are haploid. (There is only a single copy of an allele or gene in the gametes.) Examples: A, a, aB, Ab, cDe, xYz

What is the difference between a genotypic ratio and a phenotypic ratio?

Genotypic ratio = the proportions of different genotypes obtained among the offspring in a cross Phenotypic ratio = the proportions of different phenotypes obtained among the offspring in a cross * can reduce ratios 2EE : 2ee = 1EE : 1ee

Who was Gregor Mendel?

Gregor Mendel (1822-1884) is considered to be the "father of genetics." He was an Austrian monk who taught science and was also trained in math.

What are the possible alleles with regard to hemoglobin?

Hb^a = normal hemoglobin Hb^s = sickle-cell hemoglobin Hba Hba = (homozygous dominant) normal hemoglobin; does not sickle when acidity level increases Hba Hbs = (heterozygous) sickle-cell trait; some red blood cells will sickle; These folks are protected from getting malaria. More about this in a minute. Hbs Hbs = (homozygous recessive) sickle-cell anemia; These folks are protected from malaria too, but that is the least of their worries because they have all the other effects I mentioned above. So, how is it that people who carry the sickle-cell allele are protected from malaria? Here is the story on this. Malaria is caused by the parasite Plasmodium that is transmitted by the bite of a certain species of mosquito. If a mosquito that carries the Plasmodium parasite bites a person, the parasites enter the person's bloodstream and seek out the red blood cells. The parasite burrows inside the red blood cells to reproduce. The parasites waste products are acidic. This increase in acidity causes the red blood cells to sickle if the person has the Hbs allele. As I mentioned earlier, any weird or odd-shaped red blood cell is sent to the spleen for destruction, and this also destroys the parasite at the same time. Clever!! Those folks that do not harbor the sickle-cell allele will suffer from malaria should they be bitten by a mosquito carrier because these people's red blood cells won't take on the crescent moon shape in response to increased acidity. Before moving on to the next item, I must tell you that the sickle-cell mutation did not occur for a reason. It didn't come about to protect people from malaria. Mutations don't happen for a reason; they just happen randomly. In this case, it is a coincidence that the parasite's waste products are acidic and cause sickling of the red blood cells resulting in both the parasites and the sickled cells being destroyed at the same time. The allele is maintained in regions where malaria is prevalent, because people who are heterozygous are better able to survive than either of the homozygotes. If two heterozygous parents have children, the odds are that a child with normal hemoglobin would be expected 25% of the time, sickle-cell trait heterozygote children would be expected 50% of the time, and a child with sickle-cell anemia would be expected 25% of the time.

Be able to perform a dihybrid cross.

In fruit flies, long wings (L) is dominant to short wings (l) and gray body (G) is dominant to ebony body (g). Problem A: Perform a cross between a pure-breeding (homozygous) long-winged, gray-bodied fly and a short-winged, ebony-bodied fly. List the genotypic and phenotypic ratio. Use FOIL: LLGG x llgg gametes= LG and lg Keep same letters together, capital 1st F1= LlGg Problem B: Perform a cross between two of the F1 offspring obtained in Problem A above. What is the phenotypic ratio among the F2 offspring? Use FOIL: LlGg x LlGg gametes: LG, Lg, Gl, lg, LG, Lg, Gl, lg General Rule: In a dihybrid cross with BOTH parents heterozygous for BOTH traits, a 9:3:3:1 phenotypic ratio is expected.

What is incomplete dominance? Give an example.

Incomplete dominance is a pattern of inheritance in which the heterozygote shows a phenotype that is intermediate or in between the phenotypes of either of the homozygote parents. An example is when a red flower is crossed with a white flower and all the offspring are pink. (Pink is intermediate between red and white.) The diagram that I included in those for Unit 3 shows the designation of RR for red, Rr for pink, and rr for white. This is okay as long as you remember that you are dealing with incomplete dominance, but I prefer to use the following designation because one allele is not dominant over the other: R^1 = Red allele and R^2 = White allele The possible genotypes and corresponding phenotypes would be as follows:R1R1 = Red flower R1R2 = Pink flower R2R2 = White flowerNotice that the heterozygote has the intermediate phenotype (pink, in this case). Example 1: R1R1 (red) X R2R2 (white) Take a look at the Punnett square I drew on the diagrams and overhead notes I attached to the "files" section of Canvas. You will see that the red flower parent can only pass on the R1 allele and the white flower parent can only pass on the R2 allele. Each offspring box has a combination of R1R2 and all of the offspring are pink. Example 2: R1R2 (pink) X R1R2 (pink) Here, we are crossing two heterozygotes that are pink. Take a look at the Punnett square I drew on the diagrams and overhead notes I attached to the "files" section of Canvas. Here the first pink flower parent can pass on the R1 red allele or the R2 white allele and the same goes for the second pink flower parent. When the offspring boxes are filled in the Punnett square, you will see the following: Genotypic ratio: 1 R1R1 : 2 R1R2 : 1 R2R2 Phenotypic ratio: 1 red : 2 pink : 1 white Notice that with incomplete dominance, the phenotypic ratio matches up exactly with the genotypic ratio. You can tell what the flower's genotype is by looking at its phenotype. [1:2:1 for both]

Be able to describe/draw the processes of meiosis I and meiosis II. (See diagrams drawn in class.)

Meiosis I involves the reduction division where the number of chromosomes is reduced by half. Meiosis II involves the separation of sister chromatids. Features of meiosis: a) two nuclear divisions to complete the process b) homologous chromosomes separate first, then the sister chromatids separate c) diploid (2N) ----> haploid (N) d) produces four daughter cells that are different from the parent cell and different from each other * first three stages are the same as mitosis

Define meiosis. Where does it occur in the body?

Meiosis is nuclear division for the production of sex cells (eggs and sperm). Meiosis only occurs in the ovaries of females and the testes of males.

What is the particulate theory of inheritance?

Mendel proposed the particulate theory of inheritance. (This is in opposition to the blending hypothesis.) The particulate theory states that genes are inherited and passed on as discrete units.

Be able to describe/draw the process of mitosis. Are the daughter cells identical to the parent cell?

Mitosis is ordinary nuclear/cell division for growth, repair and replacement of old worn out cells. (See diagrams drawn in class) Features of mitosis- body cells: a) only one nuclear division during the process b) sister chromatids separate c) diploid (2N) ----> diploid (2N) d) produces two daughter cells that are identical to the parent cell and to each other

How do genes and the environment affect phenotype?

Most of our genetic traits are not 100% genetic. Both genes and the environment work together to determine the phenotype. Even traits like height can be affected by the environment. You could inherit genes for the potential to be really tall, but if you don't get enough good nutrition to feed your body during critical growing years, you may not realize your full potential as far as height is concerned and be somewhat stunted in your growth. We know that skin color can be affected (temporarily) by how much time you spend out in the sun. ex: temperature effects Himalayan rabbits coats, sex of some reptiles Acidity or Alkalinity of soil and flower color

What are multiple alleles? Give an example. Be able to do some genetics problems involving ABO blood types.

Multiple alleles = There are more than two alternative alleles for a given genetic trait. However, any individual can only possess a pair (two) alleles for the trait. (Remember, genes come in pairs just like Levis come in pairs.) A and B are dominant over O A and B are codominant

Offspring of sexually-reproducing organisms do not resemble either parent exactly. Explain.

Offspring of sexually-reproducing organisms do not resemble either parent exactly because they receive half of their genes from each parent. The offspring will show some genetic traits from both of the parents

Define: P, F1 , and F2 generations

P generation = the parental generation (Typically, when you see the P generation listed as such, it indicates that the parents are pure-breeding.) (Parents) F1 generation = the first filial generation = the first generation of offspring (obtained by crossing two members of the P generation) (Kids) F2 generation = the second filial generation = offspring obtained from crosses of F1 individuals (Grandkids) Note: There also can be F3, F4, etc. generations

What is pleiotropy? Give an example.

Pleiotropy is a term used to describe an allele that affects more than one characteristic or trait. All of the genes/alleles we have talked about so far have only affected one aspect of a phenotype. If you inherit "E," then you would have unattached earlobes. The "E" allele doesn't affect any other additional trait other than your earlobe shape. This is not the case with pleiotropy. With pleiotropy, a single pair of genes/alleles is inherited and we will see multiple effects on the phenotype. Example 1: Marfan Syndrome People with Marfan Syndrome are tall (over six feet tall), thin, have long arms and legs, have long fingers and toes, are nearsighted, and have a weak wall of the aorta (the largest artery in the body). This is what I meant by multiple effects on the phenotype because of a single pair of genes/alleles. This may seem like an odd combination of traits, but there is a common thread that ties it all together. The pair of alleles responsible for Marfan Syndrome causes a problem with how connective tissue is formed. All the items I listed above have to do with connective tissue/cartilage/bone. There is a lot of connective tissue in eyes. You know how tough they are if you have ever had to dissect an eye. The nearsightedness associated with Marfan Syndrome is because the eyeballs are football shaped, rather than more round, and the images are not focused on the retina. There is also a lot of elastic connective tissue in the aorta because it must withstand the blood pressure when the left ventricle of the heart pumps blood to all parts of the body. Example 2: Sickle-Cell Anemia Sickle-cell anemia is a genetic disease where the red blood cell hemoglobin protein that carries the oxygen takes on a stiff rod shape when the acidity of the blood increases. The acidity of blood will increase when we exert ourselves through exercise or just going about normal activities like climbing a flight of stairs, walking across campus, etc. The carbon dioxide that we produce as a waste product is carried as carbonic acid in our blood. It is this acid that causes the hemoglobin to form a stiff rod, and this makes the normally biconcave disc shaped red blood cells take on a crescent moon shape.When blood cells are shaped like crescent moons, they get caught and hook onto each other clogging up the small blood vessels and capillaries. This disrupts the delivery of oxygen to the tissues. This can cause debilitating pain and muscle cramping. People with sickle-cell anemia cannot do normal activities like riding a bicycle, climbing a flight of stairs, playing out in the yard or participating in sports. Most people who carry the sickle cell allele are of African or Mediterranean descent. It is this region where the mutation likely arose. Back to the initial discussion of pleiotropy, some of the multiple effects of inheriting two copies of the recessive sickle-cell anemia alleles are: lack of oxygen to tissues, muscle cramping, anemia (because our bodies send weird-shaped red blood cells to the spleen to be destroyed), kidney damage, problems with lungs, and other vital organs, etc.

What is polygenic inheritance? Give examples of traits that exhibit polygenic inheritance.

Polygenic inheritance is a pattern of inheritance where the genetic traits are controlled or determined by several pairs of genes/alleles rather than just one pair of gene/alleles. Polygenic inheritance is also called additive or quantitative inheritance because each contributing allele adds a bit more to the expression of the trait.

How is color-blindness inherited? Be able to do some problems dealing with color-blindness.

Red-green colorblindness is an X-linked recessive allele on the X chromosome.

What are sex chromosomes? What sex chromosomes in humans determine femaleness? What sex chromosomes in humans determine maleness?

Sex chromosomes determine the sex (gender) of the organism. Humans have one pair of sex chromosomes. Females have a pair of X chromosomes (XX) usually. Males have one X chromosome and one Y chromosome (XY) usually. The X chromosome is a lot larger than the Y chromosome. The X chromosome carries about 300 or so genes on it. The Y chromosome doesn't have near that many, but there is one gene in particular on the Y chromosome called the SRY gene. It literally "makes a man of you." The SRY gene codes for making testosterone - the male sex hormone. The SRY gene is activated about six weeks into pregnancy and floods the embryo's body with testosterone letting it develop as a male. If there is some glitch with the SRY gene and it doesn't activate and flood the embryo's body with testosterone or the gene is missing, then by default it will develop as a female. This is how you would get an XY female that would look every bit the female. You wouldn't be able to tell that she had the XY combination by looking at her outward characteristics - and if you are wondering, and I know you probably are, she would have female external genitalia too. An XX male can occur if the SRY gene happens to get spliced into one of the X chromosomes (perhaps by an error in crossing over during meiosis). When the SRY gene is activated about six weeks into pregnancy, testosterone floods the embryo's body and allows it to develop as a male. Once again, you wouldn't be able to tell he was an XX male by looking at outward physical characteristics and that goes for the external male genitalia. These occurrences are rare, but they can happen.

What is sex-influenced inheritance? What does this have to do with male pattern baldness?

Sex-influenced traits show up in both sexes, but they show up more often in one sex than the other. The alleles for these traits are on the autosomes, not the sex chromosomes. The level of certain sex hormones influences how prominent the trait is or to what extent it will be expressed. Some examples would be breast development. Females have more estrogen; therefore, we see more breast tissue in females than we do in males. (If we gave estrogen to a male though, he would develop more breast tissue. This is called gynecomastia.) We see antlers in male deer, but not the females. One of the classic examples of sex-influenced inheritance is male pattern baldness. It is a myth that you get bald genes from your mom's side of the family! You can get them from both sides of the family because these are autosomal. Freckles = autosomal. Freckles is dominant. Nonfreckled is recessive. Red-green colorblindness is X-linked recessive. Hairy ears = Y-linked. Baldness is sex-influenced. (See genotypes and corresponding phenotypes above.) BB bald in male and female Bb bald in male, not in female bb nonbald in male and female * the level of testosterone in the body along with B allele causes hair loss

Define sex-linked genes. Give some examples of X-linked traits. Give an example of a Y-linked trait.

Sex-linked genes are genes that are located on the sex chromosomes.The genes located on the X chromosome are called X-linked or sex-linked.The genes located on the Y chromosome are called Y-linked. (Note: If you ever see the term "sex-linked," it is pretty safe to assume that it means X-linked. If a gene is Y-linked, it will be specifically noted as such.) Examples of X-linked genes include: a) red-green colorblindness (persons have difficulty telling red from green; usually both these colors appear somewhat brownish to these individuals) b) hemophilia (bleeder's disease) (Individuals with this trait are missing some clotting factors.) c) Fragile-X syndrome (results in severe mental deficiency) All three traits listed above are recessive traits. Females must inherit the recessive allele on each of their X chromosomes to show these traits. This means that both the mother and the father passed on a copy of the recessive allele on the X chromosome passed on to their daughter. Females that have a copy of any of the above alleles on only one of their X chromosomes are called carriers. They can pass on the allele to their offspring, but they, themselves, do not express or show the trait.Males, on the other hand, will show the recessive traits listed above if they have the allele on their X chromosome. There is nothing on their Y chromosome that can cover up or mask these traits. Showing a recessive trait like this is called pseudodominance. Because of the fact that males will show these traits, even with one copy of the allele, means that males exhibit these traits more often than females do. Females must have two copies to show the traits. (If any of you males are red-green colorblind, you can blame your mother because she passed the X chromosome on to you. You got your Y chromosome from your dad.) X-linked dominant trait: Faulty Tooth Enamel (Individuals have tooth enamel that doesn't form properly and is very brown in color.) Both males and females will show this trait with only one copy of this dominant allele. Examples of Y-linked genes include: SRY gene (We covered this one earlier. It is the gene responsible for producing testosterone.)b) Hairy ears (I don't mean the fine peach fuzz hairs we all have on our skin. This gene causes tufts of hair to appear on the rims of the ears including the lobes. It is mainly seen in men in aboriginal tribes in New Guinea. (Probably twenty years ago, I had a student tell me he had this problem. His ears didn't look hairy, so I asked him jokingly if he shaved them. He told me that he shaved his ears every morning or else he would have ears that look like my drawing below!) Remember, only males have this because the gene is on the Y chromosome.

What are spermatogenesis and oogenesis? How many functional end products are produced by each of these meiotic processes?

Spermatogenesis = formation of sperm cells through the process of meiosis. Each round of spermatogenesis produces 4 viable/functional sperm cells. Oogenesis = formation of egg cells through the process of meiosis. Each round of meiosis produces one viable/functional egg and two or three polar bodies. Polar bodies will never develop into an egg. They disintegrate. * Has gone through 1st stage before birth * equal amts of cytoplasm at 1st meiotic division

What is the Rh factor? What must the phenotypes of the parents be for complications to arise?

The Rh factor is a separate protein that may be on the surface of red blood cells. (Rh factor was named for the Rhesus monkey because they can have this on their red blood cells too.) When you hear about the positive or negative designation with blood type, that is the Rh factor. Positive means you have it. Negative means you don't. Rh+ means you have the protein. Rh+ is dominant over Rh-. About 85% of the population is Rh+.To be Rh+, you can be homozygous (++) or heterozygous (+-). Rh- means you do not have the Rh protein on your red blood cells. About 15% of the population is Rh-. To be Rh-, you must be homozygous recessive (--). (Just a note: People who have blood type O negative are the true universal donors and those who are AB positive are the true universal recipients.) You may have heard about problems that can come about if an Rh negative mother is carrying an Rh positive baby. That means the dad had to carry the Rh positive allele because mom would have to be homozygous recessive. If the dad was homozygous for Rh positive, the couple would have heterozygous Rh positive children each time mom was carrying a child they conceived together. baby 1: no complication baby 2: mom makes antibodies that clump baby's blood * RHOgam shots given to create artificial antibodies so mom's body does not code for antibodies A positive man from Dallas Married a negative women named Alice Admidst honeymoon's glitter They'll have to consider Erythroblastosis Fetalis

Compare prokaryotic DNA with eukaryotic DNA.

The prokaryotic (bacterial) chromosome is a single loop of DNA that is located in a region called the nucleoid. Eukaryotic chromosomes exist as several to many linear segments of DNA located in the nucleus. At rest (in a nondividing cell), DNA is in the form of chromatin = a loosely arranged form of DNA. At the time of cell division, chromatin condenses into chromosomes. • The number of chromosomes can be counted. • Each species has a characteristic number of chromosomes. (Humans have 46; chimpanzees have 48; a potato has 48; a dog has 78; a fruit fly has 8; some fern plants have 1,200 chromosomes.) • The number of chromosomes that a species has is NOT a reflection of the relative advancement of the organism.

What is epistasis? Give an example.

The term epistasis means to "stand upon" or to "cover up." Epistasis occurs when one recessive pair of alleles at one locus (address on a chromosome) prevents the expression of a dominant allele at another locus. Epistasis always involves two different, nonallelic pairs of alleles and the one pair won't let the other pair (even though they are dominant) be expressed. The recessive pair of alleles "stands upon" or "covers up" the dominant allele(s) of the second pair. I have two examples for you. Example 1: Albinism Albinos are unable to produce melanin pigment in their hair and skin. Therefore, they are very pale white in color. It is not just humans that can be albino. White lab mice are albino. White rabbits (like the Easter Bunny) are albino with their white fur and pink eyes. You can look up other examples of albino animals such as pythons, deer, buffalo, alligators, etc. In some cultures, albinos got extra special treatment and they were encouraged to marry and have offspring which, you guessed it, would also be albino. Other cultures viewed albinos as something evil and they would be killed. Here is how albinism works. Example 2: Coat Color in Labrador Retrievers Here is a General Rule for epistasis: When performing a dihybrid cross with both parents being heterozygous for both pairs of alleles, and a variation on the 9:3:3:1 phenotypic ratio appears, epistasis should be suspected.

Define: inversion, translocation, deletion, duplication.

These four items fall under the category of "Changes in Chromosome Structure." a) inversion = occurs when a piece of a chromosome breaks loose, turns around 180 degrees, and rejoins in the reverse directionYou can see on the diagram that the original chromosome had a gene sequence of ABCDEFG. In the "after" part, you see that the C and D genes flip-flopped so the sequence is now ABDCEFG. As far as consequences, the C gene and the D gene are still there. They are just at the wrong locus (address) now. If a big enough section was flip-flopped or inverted, sometimes interesting contortions are seen when the homologous chromosomes pair up during meiosis, as they tend to pair up gene for gene. You may see one chromosome of the pair form a loop or a twist as they try to match up. b) translocation = when a piece of one chromosome breaks off and attaches to a different nonhomologous chromosome. c) deletion = when a piece of a chromosome breaks off and is lostOn the diagram, the "before" sequence of genes is ABCDEFG and the "after" sequence is BCDEFG. The A gene went missing. As far as consequences, it varies. If gene A codes for hair color, maybe you end up with a different hair color. That isn't a big deal. However, if gene A codes for part of the formation of your brain and you are missing those instructions - well, you get the picture. d) duplication = when a piece of a chromosome is copied two or more times in that chromosome On the diagram, the "before" gene sequence is ABCDEFG and the "after" gene sequence is ABCDEDEFG. The D and E got copied twice. Sometimes, duplications can involve hundreds of copies of the same gene(s)!

Define: polyploidy, monosomy, trisomy. Provide an example for each. What causes monosomy and trisomy to occur?

These three items fall under the category of "Changes in Chromosome Number." a) polyploidy = having more than 2 complete sets of chromosomes per cell"ploidy" means "sets"For example: Haploid = one set of chromosomes Pentaploid = five sets Diploid = two sets Hexaploid = six sets Triploid = three sets Heptaploid = seven sets Tetraploid = four sets Octoploid = eight sets b) monosomy = having only one copy of a particular chromosome This is represented algebraically by (2N - 1) meaning two sets minus one chromosome for a total of 45 chromosomes.A human example of monosomy is Turner syndrome where the female only has one X chromosome rather than two. She has a total of 45 chromosomes instead of 46. I'll give you more information about Turner syndrome when we get to Item #58. c) trisomy = having three copies of a particular chromosome This is represented algebraically by (2N + 1) meaning two complete sets plus an extra chromosome for a total of 47 chromosomes.A human example of trisomy is Down syndrome (also known as Trisomy 21) where the individual has three copies of chromosome 21 rather than the usual two copies.The cause of monosomy and trisomy is nondisjunction. Nondisjunction is the failure of chromosomes to separate properly during meiosis.

What is Mendel's Rule/Law of Independent Assortment?

This rule states that members of one pair of genes separate independently of members of a second pair of genes. All possible combinations of alleles can show up in the gametes. - no "peer pressure" - no influences

Explain how phenotypes can be altered when an individual inherits an allele that codes for a defective gene product.

Yes, indeed, phenotypes can be altered or changed when an individual inherits an allele that codes for a faulty gene product. There are all sorts of examples of this. A lot of the examples have to do with the fact that the individual cannot produce the correct protein, enzyme, or hormone. Remember that these are all types of proteins and that if a protein has the wrong shape, it probably won't work properly, if at all. Some examples are cystic fibrosis (a lethal lung disease), sickle cell anemia (a hemoglobin problem), albinism (individual cannot produce melanin), hemophilia (bleeder's disease), and many more.

Name two kinds of nuclear division.

a) Mitosis - ordinary nuclear division for growth and repair; the chromosome number remains constant; occurs in body (somatic) cells - occurs in tosies (identical cells) b) Meiosis - nuclear division for the production of eggs and sperm; the chromosome number is reduced by half; process only occurs in the ovaries of females and the testes of males [or the female and male parts of plants] - "My Oh My!"- sex

Cell division accomplishes three things. What are they?

a) Reproduction -- (usually refers to single-celled organisms) b) Growth, renewal, repair - (usually refers to multicellular organisms) c) Maintenance of an adequate surface area-to-volume ratio

What are the genotypes and symptoms of the following disorders? (Turner syndrome, metafemale, Klinefelter syndrome, XYY male)

a) Turner syndrome = female with only one X chromosome (usually shown XO where the O means zero or no chromosome to make a pair). I have included an overhead transparency page showing the karyotype and a photo of a girl with Turner syndrome. These females are short (only about 5 feet tall), have a broad shield-like chest, broad neck, congenital heart defects, nonfunctional ovaries so they don't go through puberty or have menstrual cycles, lack of breast development, and have trouble with spatial relationships. (These women would probably dislike doing jigsaw puzzles and would not want to be an architect.) They are of normal intelligence. They have a total of 45 chromosomes. b) metafemale = females with three X chromosomes (XXX). They would have a total of 47 chromosomes. Metafemales have a lot of menstrual irregularities and they go through early menopause in their early 30s. Sometimes they have a tendency toward learning difficulties. You would not be able to tell if a female was a metafemale by outward appearances. c) Klinefelter syndrome = males who have two X chromosomes and one Y chromosome (XXY). They also have a total of 47 chromosomes. I have included an overhead transparency page showing the karyotype and photo of a man with Klinefelter syndrome. These males have underdeveloped testes and some breast development (gynecomastia) because of the influence of the extra X chromosome. They have below normal intelligence. d) XYY males (also known as Jacob syndrome) = males who have one X chromosome and two Y chromosomes. The nondisjunction of the Y chromosomes happens in the father. These males are taller than average (over six feet tall), have persistent deep cystic acne because of extra oil production in the skin, and barely normal intelligence. There is a myth that these XYY males are more aggressive and have criminal tendencies. Any increased aggression might result from extra testosterone that is produced. As far as criminality, there is no evidence to back this up. It used to be that parents and teachers were told that boys with the XYY genotype were "born criminals." In some cases, this may have been a self-fulfilling prophecy. If someone tells you that you are going to end up as a criminal and your teachers and others are told about this, then some of these boys may have figured that was their fate. (With the barely normal intelligence, if they did commit misdeeds, it is possible they didn't know any better.)

The type of information that can be learned from examining a karyotype is:

a) sex (gender) - whether the individual is male or female b) if there are extra or missing chromosomes (such as Trisomy 21 or Turner syndrome females that have only one X chromosome) c) broken chromosomes (There are some genetic disorders caused by chromosomes that are missing a piece.) d) translocations (where a piece of one chromosome breaks off and goes and sticks on a different chromosome; more on this on #56 below) What you can't see on a karyotype are small things at the gene level. You can't tell what someone's eye color will be, if they have attached or unattached earlobes, what their skin color or hair color is, etc. You can only see bigger things that involve whole chromosomes (whole one missing or extra copies), bigger sections of chromosomes, or if nonhomologous chromosomes might have traded a chunk (translocation), or if the end of a chromosome has gone missing (deletion).

Recessive allele

allele that has its expression masked in the presence of a dominant allele. Recessive can refer to the alternative expression of the gene or the alternative trait. For expression of a recessive trait, two copies of the recessive alleles are required. We will use a lower-case letter to represent a recessive allele

Allele

an alternative form of a gene. (You have two alleles (genes) for every trait.)

Heterozygous

having two different alleles (Tt) for a given trait. Heterozygotes are known as hybrids (Liger {lion and tiger})- can't have offspring because half chromosomes are from different animals; can't match up in cross

Homozygous

having two identical alleles for a given trait. The pairs of alleles will be both dominant (TT) or both recessive (tt)

Genotype

the set of genes or alleles possessed by an organism. The genotype remains constant throughout the life of the organism. (TT, Tt, and tt are genotypes.)

Explain the significance of Mendel's experiments compared to the experiments of others before him. (What things did Mendel do that allowed him to come to the conclusions that he did?)

• Mendel did most of his work on garden peas around 1860. • Peas are easy to grow and have a short generation time. • Mendel gathered data and analyzed it statistically. • Mendel spent about two years making sure he had true- breeding peas. (This means the offspring would show the same traits as the parents.) • Mendel kept accurate and detailed records of the inheritance of seven traits in peas.