Genetics and Inheritance (Human Genetic Disorder) (5)

Genetically modified (GM)

-An organism whose genetic material has been altered through some genetic engineering technology or technique. -Foods that are produced from genetically modified organisms

Carriers/recessive disorders/recessive allele

-Family members with only one copy of the recessive allele are said to be carriers. Recessive disorders can be easily identified in the pedigree because they skip generations. Red-green color blindness is a common sex-linked recessive disorder passed on to children through the mother's X chromosome. -For recessive traits, if an individual is known to have a heterozygous genotype, meaning he or she has one allele that codes for the trait and one that doesn't, the shape is only colored in halfway. This indicates that the individual doesn't display the trait but does have a single recessive allele that he or she can pass to offspring. Sometimes this individual is called a "carrier."

Aneuploid

-Having too many or too few copies of a particular chromosome -describes an organism with more or less than the appropriate number for the species Examples: -trisomy 21 (Down syndrome) results when there are three copies of chromosome 21 present. This occurs when the sister chromatids fail to separate during meiosis, and one of the gametes has two copies of chromosome 21, but the other has none. -Turner syndrome, where women only have one copy of the X chromosome. -Klinefelter Syndrome, which is characterized by having two copies of the X chromosome, in addition to one Y chromosome. *Down, Turner, and Klinefelter syndromes all have associated phenotype changes

Pedigrees

-In biology, a pedigree is a family tree showing which family members have the genes for a certain trait. -In a pedigree, females are shown with circles and males are shown with squares. -Individuals that have the trait are shown with the shape colored in, and individuals that don't have the trait are shown with the shape left blank. Sometimes, especially when the trait is a genetic disease, the individuals with the trait are called "affected individuals." -For recessive traits, if an individual is known to have a heterozygous genotype, meaning he or she has one allele that codes for the trait and one that doesn't, the shape is only colored in halfway. This indicates that the individual doesn't display the trait but does have a single recessive allele that he or she can pass to offspring. Sometimes this individual is called a "carrier." -Remember that there can't be a carrier for a dominant trait. If an individual has one gene for the dominant trait, he or she is an affected individual. -When two individuals mate and have offspring together, this is shown with a horizontal line connecting the parents and a vertical line coming down from it to the offspring's generation. -Each offspring comes down on a branch from that line. In this example of a pedigree showing a dominant trait, the female parent is unaffected, and the male parent is affected. They have three offspring — an affected female, an unaffected female, and an unaffected male. -If the offspring mate and have their own offspring, the pedigree again shows a horizontal line from the individual to his or her mate, who presumably isn't closely related to the other individuals on the tree. -Pedigrees can sometimes be used to determine whether a trait is dominant or recessive. It's often easiest to do this by starting with the offspring and determining what genotype the parents must have had. -For example, in this pedigree, if the trait was dominant, for the children to have inherited the trait, they must have inherited an allele for the trait from at least one parent. -However, the parents couldn't have any alleles for the trait. If they did, they would be affected by the trait. -So, the trait can't be dominant. Check if it can be recessive. For some of th

Pedigree to study family records

-Mendel's studies with peas were a simple, quick, and elegant way to study inheritance. However, such studies can't be conducted in humans. Instead, geneticists study family records and the pedigree, or family tree, of people using a set of standard symbols. -Using these symbols, Mendel's laws of inheritance can be studied in humans. Patterns of inheritance of both autosomal and sex-linked traits, including genetic disorders, can be drawn in the form of a family tree and examined.

Nondisjunction Errors (Zygotes)

-Nondisjunction errors occur when homologous chromosomes or sister chromatids fail to separate during meiosis. -Recall that meiosis results in four haploid daughter cells. This means that each daughter cell has half the number of chromosomes as did the parent cell. Fertilization of the daughter cells with another haploid gamete results in the formation of a diploid zygote. -If homologous chromosomes fail to separate properly in meiosis I, a gamete can have too many or to few chromosomes. Fertilization of these daughter cells with a haploid gamete results in the formation of an aneuploid zygote. Aneuploid means that the cell has an atypical number of chromosomes. Notice that the fertilized zygotes in this case have either three sets or only one set of chromosomes instead of two. -Similarly, if sister chromatids fail to separate properly in meiosis II, a gamete can have too many or too few chromosomes. Fertilization of these daughter cells with a haploid gamete again forms an aneuploid zygote. Again, these fertilized zygotes have either three sets or only one set of chromosomes instead of two. -The lack of separation of homologous chromosomes or sister chromatids in nondisjunction errors means that the extra chromosome or missing chromosome will be present in every cell of the offspring's body. Missing autosomal chromosomes are lethal to the cell and/or embryo. Many, but not all, autosomal trisomies are also lethal. -Trisomy 21, having three copies of chromosome 21, is commonly known as Down syndrome. Trisomy 21 is the most common trisomy of embryos that survive to birth, affecting about 5,000 babies born each year.

Human Karyotype (image)

-Notice the difference in the sex chromosomes. The human male has both an X and a Y chromosome, the X from the female parent and the Y from the male parent. The female has two X chromosomes.

Pedigree of a family with a sex-linked recessive disorder (image)

-Pedigree of a family with a sex-linked recessive disorder. A female carrier and an unaffected man have three children: one unaffected male, and two female carriers. One of the females in generation two has children with an unaffected male. In the five children in the third generation, one female is unaffected, two males are affected, one female is a carrier, and one male is unaffected

Genotype/Phenotype/homozygous/heterozygous/allele review

-Recall that an organism's genotype, its genetic composition, gives rise to its phenotype, which is its observable characteristics. Each genotype is associated with a specific phenotype. Because of variations in a gene, a single gene can produce many different phenotypes. These variations of a gene are called alleles. Recall that Mendel observed seven phenotypic traits, including the shape of peas (round or wrinkled) and the color of the flowers of the pea plant (purple or white). These observable characteristics are encoded in the plant's DNA and are examples of phenotypes. Different versions, or alleles, of each gene produce various phenotypes. -Also, recall that individuals with two copies of the same allele are homozygous for that gene. Individuals who have two different alleles for a given gene are heterozygous for that gene.

The Human Genome Project

-Scientists continue to unlock the mysteries of DNA in the laboratory. The success of the Human Genome Project at the beginning of the twenty- first century paved the way for more discoveries related to DNA and genetics research and introduced new ethical quandaries. -The Human Genome Project took 13 years to complete. This project launched in 1990 with two goals: 1 - to sequence all base pairs of human DNA 2 - To identify all human genes

Genetically modified organisms

-While humans have used selective breeding for millennia to grow crops and livestock with desired characteristics, genetic engineering is now used to alter the DNA sequences of organisms specifically and rapidly. -Genetically modified (GM) foods are produced from genetically modified organisms, often abbreviated GMOs. The first GMO produce became available to consumer in the mid-1990s, and in 2015, a genetically modified salmon became the first GM animal to be approved for food in the United States. -Much of the corn, soybeans, canola, alfalfa, and sugar beets grown in the United States are genetically modified and used as animal feed or as ingredients in other foods. -The World Health Organization and the United Nations have worked together to create safety standards for genetically modified foods, and there are specific regulations dictating how genetically modified foods are labeled in many countries. Beginning in 2022, the USDA will require genetically modified foods to be labeled in the United States. -Some genetic modification makes alterations to the organism's existing genome, without adding additional genes. Others involve adding genes from other organisms. -Transgenic organisms possess not only their original DNA, but also the genes of other organisms. An example of a useful transgenic organism is golden rice. In many places in the world where rice is a staple food, vitamin A deficiency is common and can lead to death or to irreversible blindness. -Beta-carotene is a precursor to vitamin A, which rice plants naturally make, but don't normally produce in the edible part of rice. Two beta-carotene biosynthesis genes, one from a daffodil and one from a soil-bacterium, were used to get the rice to create beta-carotene in the edible part of the rice. This transgenic organism has the potential to solve a major health crisis. -Genetic modification has been a tool used to fight many problems in crops, including preventing damage from pest insects, managing pest weeds, increasing yield, increasing nutritional value, increasing shelf life, and providing resistance to stress and release. Genetic modification has also created organisms useful for producing drugs, producing biofuel, and absorbing toxins in biore

Autosomal Genes/recessive/dominant/generational skips

-all other genes except for sex-linked genes -Autosomal genes follow a simple pattern of inheritance as defined by Mendel's law of dominance, which establishes that dominant traits will be expressed over recessive traits. Autosomal dominant alleles lead to the expression of the allele, whether the individual has one or two copies of the allele. Autosomal recessive alleles are only expressed when the individual is homozygous for the recessive allele. However, people who only have one copy of the recessive trait are carriers of the trait and could pass the recessive allele on to future generations. A trait or disease can be identified as autosomal dominant or autosomal recessive using a pedigree. Autosomal dominant disorders typically don't skip generations, while autosomal recessive traits do skip generations.

Euploid

-an individual/organism with the appropriate number of chromosomes for their species

Karyotype

-is an organized profile of an organism's chromosomes. It's a way to characterize the chromosomes located in the nucleus of a eukaryotic cell. -___?___s reveal many important characteristics of an organism's chromosomes, such as the number, relative size, shape, and appearance of the chromosomes.

Nondisjunction

-is the failure of sister chromatids to separate during meiosis. This results in the gametes having the wrong number of chromosomes for the species.

Transgenic Organisms

-organism that contains genes from other organisms --Transgenic organisms possess not only their original DNA, but also the genes of other organisms. An example of a useful transgenic organism is golden rice. In many places in the world where rice is a staple food, vitamin A deficiency is common and can lead to death or to irreversible blindness.

Affected individuals

-shaded square or circle -Sometimes, especially when the trait is a genetic disease, the individuals with the trait are called "affected individuals."

Karyograms

-shows chromosomes of an organism in homologous pairs of decreasing length (chromosomes are best seen during metaphase with a stain, some stains provide distinctive banding pattern for each chromosome) -Geneticists use karyograms to identify and diagnose chromosomal aberrations that may result in a genetic disorder. An organism with too many or too few chromosomes is the easiest aberration to identify. The term euploid describes an organism with the appropriate number of chromosomes for the species, and aneuploid describes an organism with more or less than the appropriate number for the species. As discussed earlier, trisomy 21 (Down syndrome) results when there are three copies of chromosome 21 present. This occurs when the sister chromatids fail to separate during meiosis, and one of the gametes has two copies of chromosome 21, but the other has none. Other examples of aneuploidism are Turner syndrome, where women only have one copy of the X chromosome, and Klinefelter Syndrome, which is characterized by having two copies of the X chromosome, in addition to one Y chromosome.

Multifactorial traits (Complex)

-traits that result from the interaction of one or more environmental factors and two or more genes -In addition to Mendel's laws governing inheritance, non-Mendelian inheritance patterns also have been observed. Complex or multifactorial traits, for example, can give rise to a variety of phenotypes because of gene interactions and interactions between genes and their environment.

Down/Turner/Klinefelter syndromes

-trisomy 21 (Down syndrome) results when there are three copies of chromosome 21 present. This occurs when the sister chromatids fail to separate during meiosis, and one of the gametes has two copies of chromosome 21, but the other has none. Other examples of aneuploidism are Turner syndrome, where women only have one copy of the X chromosome, and Klinefelter Syndrome, which is characterized by having two copies of the X chromosome, in addition to one Y chromosome. -Down, Turner, and Klinefelter syndromes all have associated phenotype changes. Down syndrome occurs in 1 out of every 800 to 1000 live-born infants. Individuals with Down syndrome have a characteristic facial appearance and learning difficulties. Turner syndrome alters development in the female, often causing infertility due to lack of ovarian function, short stature, skeletal abnormalities, heart defects, and kidney problems. Turner syndrome occurs in about 1 in 2,500 female births, but it's more common that pregnancies end before going to term. Klinefelter syndrome occurs in 1 out of every 500-1000 newborns. Klinefelter syndrome causes infertility in males, and there are frequently physical changes such as abnormal body proportions, tall stature, less facial hair, and small male reproductive organs. While these genetic disorders have some characteristic phenotypes, they can most easily be confirmed through karyograms.

Scientists have learned the following from the Human Genome Project:

1 - The human genome contains three billion nucleotide bases. 2 - Two percent of the human genome is genes that code for proteins. Many chromosomes have large stretches without genes. 3 - Much of the human genome is a result of genetic code from viruses. Genes are linked to certain diseases and disorders. There are three million locations where a single base pair is different in humans. *These findings resulted in new questions about the ethical, legal, and social implications of privacy and the use of genetic information. Future sequencing research can exploit the human genome to better understand how to treat diseases.

Biotechnology

A form of technology that uses living organisms, usually genes, to modify products, to make or modify plants and animals, or to develop other microorganisms for specific purposes.

genetic engineering / genetic modification

A technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally.

DNA in mitochondria

Also, small DNA molecules found in the mitochondria can pass from a mother to her child with few changes, and this mitochondrial DNA can be compared.

Biomedical Advances Raise Ethical Questions (12/15)

As scientific studies lead to a better understanding and isolation of certain genes, new organisms can be created and modified to fit certain criteria. This often leads to questions about whether this work is justified. What if these powers landed in the hands of those with malicious intent? Or, what if science created an organism that could destroy mankind? With so many pros and cons on each side of the controversy over genetic engineering, you must become familiar with these issues to answer important questions that may shape the future as you know it.

DNA as a personal identification

Aside from identical twins, no two humans have the same genetic makeup. DNA fingerprinting has been used to take advantage of this fact. Forensics, often glorified by television shows, is the study of a crime scene. Forensics uses DNA fingerprinting to overturn unjust convictions, but it can't yet be used to convict an individual. The difference of one or two base pairs is enough to say that someone did not commit a crime, but a match isn't unequivocal evidence. When DNA is sequenced for forensics, it isn't the entire organism's genome, so a match may or may not be a coincidence. DNA forensics also can be used to identify organisms in conservation practices. Paternity testing is one of the most important uses of DNA fingerprinting. Because Y chromosomes are never altered through the process of crossing over, very few changes result when passed from father to son. Also, small DNA molecules found in the mitochondria can pass from a mother to her child with few changes, and this mitochondrial DNA can be compared.

Germline mutations / Acquired mutations

Besides errors occurring in meiosis, genetic mutations in the fertilized embryo can be germline mutations or acquired mutations. Sometimes, a mutation may occur in a person's germ cells but not other cells. These mutations can be passed on to the person's children.

Luther Burbank / selective breeding

Breeding organisms that result in offspring with desired characteristics is referred to as selective breeding. Selective breeding can produce new varieties of plants and animals. Luther Burbank was a botanist who took advantage of hybridization to make plants that exemplified the best traits from each parent. He produced disease-resistant hybrids that could make more food.

Selective Breeding

Breeding organisms that result in offspring with desired characteristics is referred to as selective breeding. Selective breeding can produce new varieties of plants and animals. Luther Burbank was a botanist who took advantage of hybridization to make plants that exemplified the best traits from each parent. He produced disease-resistant hybrids that could make more food.

Cloning

Cloning is another application of genetic engineering. Here, a single cell can be used to produce new cells, tissues, or even full organisms. In organismal cloning, the nucleus of an egg cell is removed and fused with a donor nucleus. As this grows into an embryo, it can be implanted in the uterus of a foster mother.

Diagnosing genetic conditions:

Diagnosing genetic conditions can be difficult because genes related to a particular disease may exhibit mutations, but scientists and doctors don't yet know enough about the disease to know the exact role of the gene in the disease, or if there's any direct role at all. Sometimes, no mutations are found in a gene known to cause a disease, but a mutation may exist on a related gene. The human genome has about 24,000 genes, and scientists don't yet understand the roles of all these genes in human health and disease.

Process of X inactivation:

Early in embryonic development, each of the cells inactivates one X chromosome, and it's random which one it is. As the cells reproduce to build the body structures, the cells they create maintain the same Barr body (inactive X chromosome) and X chromosome. You can see this in the color of a tortoiseshell or calico cat's fur. A gene that affects fur color is coded in a cat's X chromosomes; if the gene is present, the fur becomes orange or another light color, and if the gene is absent, the fur is black. If a female cat is heterozygous for the gene, one X chromosome has it and the other X chromosome lacks it; there will be some patches of fur in which the X chromosome that has the gene is inactivated, making black fur, and some patches in which the X chromosome that lacks the gene is inactivated, making orange fur. This creates the mottled tortoiseshell pattern. Because it results from X- inactivation, this means that all tortoiseshell cats are female.

Genetic Testing & ethical issues

Genetic testing is a way for individuals to find out more about their genetic makeup and can diagnose many disorders. People often use genetic testing to determine if they're carriers of a gene associated with a disease that could potentially be passed on to future children. The ethical issues involved with genetic testing involve the fact that the roles of genes in disease remain poorly understood. Another ethical issue involved with genetic testing is the fact that one's genetic results have implications for one's family. Learning that a relative is a carrier for a serious genetic defect could cause psychological issues in other relatives, who may fear that they are carriers of the gene. Or the lack of a genetic marker for one type of disease may lead to less vigilance in taking appropriate precautions for another, unrelated disease.

Autosomes

Humans have 46 chromosomes, 22 pairs of chromosomes called ___?___ which are any chromosomes that aren't sex chromosomes, and one pair of sex chromosomes

Chromosome errors (Down syndrome)

If chromosomes fail to separate and shuffle properly into the gametes during meiosis, an egg or sperm cell can have too many or too few chromosomes. This lack of separation means that the extra chromosome will be passed down to the offspring and be present in every cell of the offspring's body. The word "trisomy" means that there are three copies of a chromosome, rather than just two—one from a person's mother and one from the father. Trisomy 21, having three copies of chromosome 21, is commonly known as Down syndrome. Trisomy 21 is the most common chromosomal anomaly and affects about 5,000 babies born each year.

Small changes in DNA Molecules Can Affect human traits

Importantly, genes themselves aren't the cause of disease. Instead, genetic disorders result when a mutation renders a gene and its protein product unable to function properly. Every human has a version of each gene; however, some people have mutated versions of genes that give rise to diseases. For example, consider the BRCA1 and BRCA2 genes which, in their normal function, repair cell damage and keep breast and other tissues healthy. People with a mutation in the BRCA1 and/or BRCA2 genes are much more likely to develop breast cancer and other cancers than the general population. However, BRCA1 and BRCA2 mutations are uncommon in the general population, occurring in about 1 in 400 people. The prevalence of certain genetic mutations can vary by ethnic group; for example, in the Ashkenazi Jewish population, about 1 in 40 have a BRCA1 and/or BRCA2 mutation. It's uncommon for a genetic mutation to cause disease. However, other types of genetic changes occur more frequently. Genetic changes that occur in more than one percent of the population are known as genetic polymorphisms. Some genetic mutations do have positive effects; for example, a beneficial mutation may be a change in DNA producing a protein that protects against a certain bacteria or virus. Diagnosing genetic conditions can be difficult because genes related to a particular disease may exhibit mutations, but scientists and doctors don't yet know enough about the disease to know the exact role of the gene in the disease, or if there's any direct role at all. Sometimes, no mutations are found in a gene known to cause a disease, but a mutation may exist on a related gene. The human genome has about 24,000 genes, and scientists don't yet understand the roles of all these genes in human health and disease.

Sex-linked recessive disorder

In a sex-linked recessive disorder, the only people who exhibit the disorder have one or two copies of the recessive allele without a dominant allele to mask it. Sex-linked disorders are only passed on via either the X or Y chromosome. Sons inherit only one X chromosome from their mothers, while daughters obtain an X chromosome from each parent. Therefore, if a mother exhibits a sex-linked recessive disorder, indicating that both X chromosomes are affected, 100 percent of her sons will inherit a mutated X chromosome and exhibit the sex-linked recessive disorder because they don't have another X chromosome to mask it. If a mother is a carrier for a sex-linked recessive disorder, each son has a 50 percent chance of being affected by the disease and a 50 percent chance of inheriting only the unaffected chromosome. Because daughters receive an X chromosome from each parent, daughters will only exhibit a sex-linked recessive disorder if they receive the mutated allele from both of their parents.

Autosomal Dominant disorder:

In an autosomal dominant disorder, if one or both alleles are mutated, the individual will exhibit the disorder. Heterozygous individuals with the disorder have a 50 percent chance of passing the mutated allele to each child, making that child exhibit the disorder. Individuals homozygous for the mutated allele will pass a mutated allele to every child, making 100 percent of their children exhibit the disorder. Note that there are no carriers in a dominant disorder. Because the mutated allele is dominant, all individuals with a mutated allele will exhibit the disorder, even if they inherited an unaffected gene from the other parent. The neurological disorder Huntington's disease, marked by the progressive breakdown of nerve cells, is an example of an autosomal dominant disorder.

De novo mutations

In another case, a mutation can occur in the germ cell right after the formation of the zygote. Such mutations occurring in the embryo will manifest in all the embryo's growing cells. These are called de novo mutations and explain why a child can have a mutation with no history of the mutation or the resulting disorder in their parents or other ancestors.

Mutation in the germ cell

In another case, a mutation can occur in the germ cell right after the formation of the zygote. Such mutations occurring in the embryo will manifest in all the embryo's growing cells. These are called de novo mutations and explain why a child can have a mutation with no history of the mutation or the resulting disorder in their parents or other ancestors.

Meiosis / cell division / defective genes

In humans and other eukaryotic organisms, meiosis is a type of cell division that produces germ cells. Germ cells are egg and sperm cells. They can contain defective genes that result in miscarriages or cause genetic disorders. Errors made by the cellular machinery during meiosis can lead to serious genetic disorders. Some typical errors include incorrect copying of the DNA sequence when the DNA is replicated before cell division, errors during recombination, or errors when chromosomes segregate to the daughter cells.

Act passed into law in 2008

In the United States, the armed services collect DNA to identify a body if the worst should happen. However, what if your DNA was used to determine how you could live your life? An act was passed into law in 2008 to protect all Americans from discrimination based on their genetic information.

Inbreeding

Inbreeding is a type of selective breeding that occurs when individuals with similar characteristics continue to be bred to keep a certain set of traits. This makes inbred organisms genetically similar, and the probability that members of the population will receive mutated alleles leading to disorders is high.

Polymorphisms

It's uncommon for a genetic mutation to cause disease. However, other types of genetic changes occur more frequently. Genetic changes that occur in more than one percent of the population are known as genetic ___?___. Some genetic mutations do have positive effects; for example, a beneficial mutation may be a change in DNA producing a protein that protects against a certain bacteria or virus.

Karyotypes purpose in biology:

Karyotypes can be used for a variety of purposes in biology and genetics. They may provide information about chromosomal aberrations, cellular function, taxonomic relationships, and past evolutionary events.

Profits and privacy

New ethical considerations often come with advancement and change. For example—"Who owns your genes?" Do you have exclusive rights to the genetic makeup found inside you? Should anyone be able to investigate your genetic makeup? In the United States, the armed services collect DNA to identify a body if the worst should happen. However, what if your DNA was used to determine how you could live your life? An act was passed into law in 2008 to protect all Americans from discrimination based on their genetic information.

Paternity Testing

Paternity testing is one of the most important uses of DNA fingerprinting. Because Y chromosomes are never altered through the process of crossing over, very few changes result when passed from father to son. Also, small DNA molecules found in the mitochondria can pass from a mother to her child with few changes, and this mitochondrial DNA can be compared.

Pedigree of a family with an autosomal dominant disorder (image)

Pedigree of a family with an autosomal dominant disorder. An unaffected woman and an affected man in the first generation have three children who are all affected. One of them has children with an unaffected person, and three of five of their children are affected by the disorder

Chromosomes / Autosomes

Recall that a chromosome is a molecule of DNA that contains part or all of an organism's genetic material. It's a threadlike structure of DNA that's tightly coiled and packaged. Humans have 46 chromosomes, 22 pairs of chromosomes called autosomes which are any chromosomes that aren't sex chromosomes, and one pair of sex chromosomes. There are two types of sex chromosomes, X and Y. Females have two X chromosomes as their sex chromosomes, so they can only pass an X chromosome to their children. Males have one X and one Y chromosome as their sex chromosomes, so they can pass on either of their sex chromosomes, which determines the child's biological sex. The male parent contributes a Y chromosome to male offspring and an X chromosome to female offspring.

Centromere

Region of a chromosome where the two sister chromatids attach

Genetically modified and cloned organisms

Scientists can directly manipulate the genes of organisms using biotechnology, a set of processes known as genetic engineering or genetic modification. The goal of genetic modification is to change a specific trait without affecting the rest of the organism's genome, and it is often done to improve crops.

Sex linkage inheritance:

Sex linkage is a characteristic pattern of inheritance exhibited by genes located on a sex chromosome. Females have two copies of the X chromosome, so they can be either homozygous or heterozygous for a sex-linked allele on the X chromosome. Males, however, only have one X chromosome, so they express the alleles present on that X chromosome. Because they have one X and one Y chromosome, the concept of "dominant" or "recessive" doesn't apply to males' sex chromosomes.

Shotgun sequencing

Shotgun sequencing is a genomic sequencing method that was able to help the Human Genome Project in its pioneering goals. Shotgun sequencing is used to determine the genetic sequences of long strands of DNA. First, DNA is randomly broken up into many small fragments, and each fragment is sequenced. Then, a computer program is used to reassemble the DNA fragments. Scientists were able to sequence a copy of DNA in a human by using shotgun sequencing to sort and piece together the complete human genome. Bioinformatics enabled this progress, as computers were used to collect, organize, and interpret data.

Mosaicism

Some types of mutations that occur early in the embryo's development can result in two forms of DNA existing in the cells of the body. The different forms of DNA occurring in the body are the result of cell division occurring before and after the mutation. This is known as mosaicism, which is a condition that can cause health problems, depending on the mutation and how many cells are affected by the mutation. Sometimes, genetic mutations can be so severe that they fatally disrupt embryonic development.

Mutations that occur early in the Embryos development: -> 2 forms of DNA

Some types of mutations that occur early in the embryo's development can result in two forms of DNA existing in the cells of the body. The different forms of DNA occurring in the body are the result of cell division occurring before and after the mutation. This is known as mosaicism, which is a condition that can cause health problems, depending on the mutation and how many cells are affected by the mutation. Sometimes, genetic mutations can be so severe that they fatally disrupt embryonic development.

The Human Genome Project 2 goals:

The Human Genome Project took 13 years to complete. This project launched in 1990 with two goals: 1 - To sequence all base pairs of human DNA 2 - To identify all human genes

The patterns of inheritance of a gene are dependent upon:

The patterns of inheritance of a gene are dependent upon whether the allele is on an autosomal or sex chromosome, and whether the allele is recessive or dominant.

Trisomy

The word "trisomy" means that there are three copies of a chromosome, rather than just two—one from a person's mother and one from the father. Trisomy 21, having three copies of chromosome 21, is commonly known as Down syndrome. Trisomy 21 is the most common chromosomal anomaly and affects about 5,000 babies born each year.

Sex Chromosomes (X & Y)

There are two types of sex chromosomes, X and Y. Females have two X chromosomes as their sex chromosomes, so they can only pass an X chromosome to their children. Males have one X and one Y chromosome as their sex chromosomes, so they can pass on either of their sex chromosomes, which determines the child's biological sex. The male parent contributes a Y chromosome to male offspring and an X chromosome to female offspring.

Creating a Karyotype

To create a karyotype, scientists must image chromosomes from a cell. A karyogram is an image of chromosomes arranged by size and other characteristics. Karyotypes can reveal information about the sister chromatids, the identical copies of each chromosome that the centromere joins together. The karyotypes also reveal the location of the centromeres, or the location where the sister chromatids are closest together.

Tortoiseshell Cats and Chromosomes

Tortoiseshell cats display a mottled red and black coat caused by X chromosomes being inactivated differently in different cells. Early in embryonic development, each of the cells inactivates one X chromosome, and it's random which one it is. As the cells reproduce to build the body structures, the cells they create maintain the same Barr body (inactive X chromosome) and X chromosome. You can see this in the color of a tortoiseshell or calico cat's fur. A gene that affects fur color is coded in a cat's X chromosomes; if the gene is present, the fur becomes orange or another light color, and if the gene is absent, the fur is black. If a female cat is heterozygous for the gene, one X chromosome has it and the other X chromosome lacks it; there will be some patches of fur in which the X chromosome that has the gene is inactivated, making black fur, and some patches in which the X chromosome that lacks the gene is inactivated, making orange fur. This creates the mottled tortoiseshell pattern. Because it results from X- inactivation, this means that all tortoiseshell cats are female.

X Inactivation

When it comes to sex chromosomes, having two X chromosomes would give females twice as many gene products from the X chromosome as males, unnecessarily. So, to prevent significant impacts of having an "extra" chromosome, one of the X chromosomes is inactivated. This is called X-inactivation, and the inactivated X chromosomes are called Barr bodies. Because of X-inactivation, carrying a second X chromosome doesn't impact the ability of the female to function normally.

X chromosomes

When it comes to sex chromosomes, having two X chromosomes would give females twice as many gene products from the X chromosome as males, unnecessarily. So, to prevent significant impacts of having an "extra" chromosome, one of the X chromosomes is inactivated. This is called X-inactivation, and the inactivated X chromosomes are called Barr bodies. Because of X-inactivation, carrying a second X chromosome doesn't impact the ability of the female to function normally.

Silent Mutation

While many mutations can have serious consequences, other mutations have no noticeable effects on the individual's genome. A silent mutation occurs when one DNA base in a protein-coding region is substituted for another that encodes for the same amino acid. For example, the stop codon TAA located at the end of a protein-coding sequence in DNA could experience a single mutation in the third nucleotide, rendering it TAG. The codon would remain a stop sequence, so the function of the gene would not be affected.

Bioinformatics

application of mathematics and computer science to store, retrieve, and analyze biological data

Barr bodies

inactivated X chromosomes found only in females

Karyogram

is an image of chromosomes arranged by size and other characteristics

Sister Chromatids

the identical copies of each chromosome that the centromere joins together.