Sometimes, genetic make-ups do not show up as traits. Let us assume Jane has beautiful brown eyes. Her dad has beautiful blue eyes (pure-bred blue eyes, to say, he has only blue eye genes), while her mom has beautiful brown eyes (pure-bred brown eyes, to say, she has only brown eye genes). Then Jane must be a half brown eye and a half-blue eye, but she has only brown eyes. Why and how this could happen?

Sometimes, genetic make-ups do not show up as traits. Let us assume Jane has beautiful brown eyes. Her dad has beautiful blue eyes (pure-bred blue eyes, to say, he has only blue eye genes), while her mom has beautiful brown eyes (pure-bred brown eyes, to say, she has only brown eye genes). Then Jane must be a half brown eye and a half-blue eye, but she has only brown eyes. Why and how this could happen?

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter4: Pedigree Analysis In Human Genetics

Section: Chapter Questions

Problem 1CS: Pedigree analysis is a fundamental tool for investigating whether or not a trait is following a...

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Pedigree analysis is a fundamental tool for investigating whether or not a trait is following a Mendelian pattern of inheritance. It can also be used to help identify individuals within a family who may be at risk for the trait. Adam and Sarah, a young couple of Eastern European Jewish ancestry, went to a genetic counselor because they were planning a family and wanted to know what their chances were for having a child with a genetic condition. The genetic counselor took a detailed family history from both of them and discovered several traits in their respective families. Sarahs maternal family history is suggestive of an autosomal dominant pattern of cancer predisposition to breast and ovarian cancer because of the young ages at which her mother and grandmother were diagnosed with their cancers. If a mutant allele that predisposed to breast and ovarian cancer was inherited in Sarahs family, she, her sister, and any of her own future children could be at risk for inheriting this mutation. The counselor told her that genetic testing is available that may help determine if this mutant allele is present in her family members. Adams paternal family history has a very strong pattern of early onset heart disease. An autosomal dominant condition known as familial hypercholesterolemia may be responsible for the large number of deaths from heart disease. As with hereditary breast and ovarian cancer, genetic testing is available to see if Adam carries the mutant allele. Testing will give the couple more information about the chances that their children could inherit this mutation. Adam had a first cousin who died from Tay-Sachs disease (TSD), a fatal autosomal recessive condition most commonly found in people of Eastern European Jewish descent. Because TSD is a recessively inherited disorder, both of his cousins parents must have been heterozygous carriers of the mutant allele. If that is the case, Adams father could be a carrier as well. If Adams father carries the mutant TSD allele, it is possible that Adam inherited this mutation. Because Sarah is also of Eastern European Jewish ancestry, she could also be a carrier of the gene, even though no one in her family has been affected with TSD. If Adam and Sarah are both carriers, each of their children would have a 25% chance of being afflicted with TSD. A simple blood test performed on both Sarah and Adam could determine whether they are carriers of this mutation. Would you decide to have a child if the test results said that you carry the mutation for breast and ovarian cancer? The heart disease mutation? The TSD mutation? The heart disease and the mutant alleles?
Pedigree analysis is a fundamental tool for investigating whether or not a trait is following a Mendelian pattern of inheritance. It can also be used to help identify individuals within a family who may be at risk for the trait. Adam and Sarah, a young couple of Eastern European Jewish ancestry, went to a genetic counselor because they were planning a family and wanted to know what their chances were for having a child with a genetic condition. The genetic counselor took a detailed family history from both of them and discovered several traits in their respective families. Sarahs maternal family history is suggestive of an autosomal dominant pattern of cancer predisposition to breast and ovarian cancer because of the young ages at which her mother and grandmother were diagnosed with their cancers. If a mutant allele that predisposed to breast and ovarian cancer was inherited in Sarahs family, she, her sister, and any of her own future children could be at risk for inheriting this mutation. The counselor told her that genetic testing is available that may help determine if this mutant allele is present in her family members. Adams paternal family history has a very strong pattern of early onset heart disease. An autosomal dominant condition known as familial hypercholesterolemia may be responsible for the large number of deaths from heart disease. As with hereditary breast and ovarian cancer, genetic testing is available to see if Adam carries the mutant allele. Testing will give the couple more information about the chances that their children could inherit this mutation. Adam had a first cousin who died from Tay-Sachs disease (TSD), a fatal autosomal recessive condition most commonly found in people of Eastern European Jewish descent. Because TSD is a recessively inherited disorder, both of his cousins parents must have been heterozygous carriers of the mutant allele. If that is the case, Adams father could be a carrier as well. If Adams father carries the mutant TSD allele, it is possible that Adam inherited this mutation. Because Sarah is also of Eastern European Jewish ancestry, she could also be a carrier of the gene, even though no one in her family has been affected with TSD. If Adam and Sarah are both carriers, each of their children would have a 25% chance of being afflicted with TSD. A simple blood test performed on both Sarah and Adam could determine whether they are carriers of this mutation. Would you want to know the results of the cancer, heart disease, and TSD tests if you were Sarah and Adam? Is it their responsibility as potential parents to gather this type of information before they decide to have a child?
Pedigree analysis is a fundamental tool for investigating whether or not a trait is following a Mendelian pattern of inheritance. It can also be used to help identify individuals within a family who may be at risk for the trait. Adam and Sarah, a young couple of Eastern European Jewish ancestry, went to a genetic counselor because they were planning a family and wanted to know what their chances were for having a child with a genetic condition. The genetic counselor took a detailed family history from both of them and discovered several traits in their respective families. Sarahs maternal family history is suggestive of an autosomal dominant pattern of cancer predisposition to breast and ovarian cancer because of the young ages at which her mother and grandmother were diagnosed with their cancers. If a mutant allele that predisposed to breast and ovarian cancer was inherited in Sarahs family, she, her sister, and any of her own future children could be at risk for inheriting this mutation. The counselor told her that genetic testing is available that may help determine if this mutant allele is present in her family members. Adams paternal family history has a very strong pattern of early onset heart disease. An autosomal dominant condition known as familial hypercholesterolemia may be responsible for the large number of deaths from heart disease. As with hereditary breast and ovarian cancer, genetic testing is available to see if Adam carries the mutant allele. Testing will give the couple more information about the chances that their children could inherit this mutation. Adam had a first cousin who died from Tay-Sachs disease (TSD), a fatal autosomal recessive condition most commonly found in people of Eastern European Jewish descent. Because TSD is a recessively inherited disorder, both of his cousins parents must have been heterozygous carriers of the mutant allele. If that is the case, Adams father could be a carrier as well. If Adams father carries the mutant TSD allele, it is possible that Adam inherited this mutation. Because Sarah is also of Eastern European Jewish ancestry, she could also be a carrier of the gene, even though no one in her family has been affected with TSD. If Adam and Sarah are both carriers, each of their children would have a 25% chance of being afflicted with TSD. A simple blood test performed on both Sarah and Adam could determine whether they are carriers of this mutation. If Sarah carries the mutant cancer allele and Adam carries the mutant heart disease allele, what is the chance that they would have a child who is free of both diseases? Are these good odds?
In humans, brown eyes are dominant to blue eyes, and the ability to roll your tongue is dominant to not being able to roll your tongue. If a mother who was heterozygous for eye colour and homozygous recessive for tongue rolling had a baby with a father that was heterozygous for both traits, what is the probability that their child would have blue eyes and could roll their tongue?
Tay-Sachs disease is a rare human disease in which toxic substances accumulate in nerve cells. The recessive allele responsible for the disease is inherited in a simple Mendelian manner. For unknown reasons, the allele is more common in populations of Ashkenazi Jews of eastern Europe. A woman is planning to marry her first cousin, but the couple discovers that their shared grandfather’s sister died in infancy of Tay-Sachs disease.a. Draw the relevant parts of the pedigree, and show all the genotypes as completely as possible. b. What is the probability that the cousins’ first child will have Tay-Sachs disease, assuming that all people who marry into the family are homozygous normal?
A genetic engineer is going to cross two watermelon plants to produce seeds for a spring planting. He is breeding for size, and wants to have as many watermelons with the phenotype for long shape as possible. In watermelons, the allele for short shape (R) is dominant to the allele for long shape (r). Would crossing a watermelon homozygous recessive for the trait with a watermelon heterozygous for the trait give the most long watermelons possible? Explain your answer using Punnett Squares.
In humans, the genetic disease cystic fibrosis is caused by a recessive allele (a). The normal (healthy) allele is dominant (A). What is the genotype of someone who has cystic fibrosis? What are the two different genotypes that a healthy person could have? If two people were both heterozygous for the cystic fibrosis gene, what fraction of their children would be likely to have this disease? Hint: Draw a Punnett square to figure it out.
Skin color is one of the traits in a human which is determined by polygenic inheritance system because it is possibly involving as many as 9 genes. To make this simple, let us consider the influence of 2 genes: A and B., where dark skin color is dominant. Suppose a man who is AABb marries a woman who is Aabb, what would be the genotypes of their children. Prove your answer by using a Punnet Square.
Why Geneticists Use a Variety of Symbols for Alleles ? What are those ?
In terms of dominance, why do we need to look at genetics at both organismal and the molecular level?
A man who can roll his tongue and a woman who cannot roll her tongue have a son who can roll his tongue (R = can roll tongue; r = can't roll tongue). The son is curious about whether his father is homozygous or heterozygous for the tongue-rolling trait. Which of the following facts would allow him to know? Select one: a. His paternal grandfather and his paternal grandmother can both roll their tongues. b. The son's sister is heterozygous for the trait. c. The son's own daughter cannot roll her tongue. d. His father's mother cannot roll her tongue. e. The son's sister is a tongue roller.
Skin color in humans is determined by polygenic inheritance, which means the more dominant alleles there are, the darker the skin color will be. A medium-toned skinned woman (AaBb) has a child with another medium-toned skinned man (AaBb). What is the probability of them having a very dark-toned skinned child? (Hint: the genotype is homozygous dominant)