Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 25, Problem 1PDQ
HOW DO WE KNOW?
In this chapter, we focused on a mode of inheritance referred to as quantitative genetics, as well as many of the statistical parameters utilized to study quantitative traits. Along the way, we found opportunities to consider the methods and reasoning by which geneticists acquired much of their understanding of quantitative genetics. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:
(a) How do we know that threshold traits are actually polygenic even though they may have as few as two discrete phenotypic classes?
(b) How can we ascertain the number of polygenes involved in the inheritance of a quantitative trait?
(c) What findings led geneticists to postulate the multiple-factor hypothesis that invoked the idea of additive alleles to explain inheritance patterns?
(d) How do we assess environmental factors to determine if they impact the
(e) How do we know that monozygotic twins are not identical genotypically as adults?
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In your attempts to identify a genetic basis for rheumatoid arthritis in humans, you have DNA samples from three large unrelated families in which individuals with varying
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cases from all three families.
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Rheumatoid arthritis is the result of phenocopy by the environment
Different genes regulate the disease in different families
Rheumatoid arthritis is controlled by a single X-linked recessive trait
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Rheumatoid arthritis is controlled by a single autosomal dominant trait
Phenylthiocarbamide (PTC) is an organic compound that either tastes extremely bitter or is tasteless, depending on the genotype of the taster. The tasting allele (T) is dominant over the non-tasting allele (t).
Normal skin pigmentation (N) is dominant over albinism (n).
(It is important to note that this example of PTC tasting cannot be explained with simple genetics, but for the purpose of this question, assume that it can.)
A normally-pigmented woman who cannot taste PTC has an albino father. The woman married an albino man who can taste PTC and whose mother cannot taste PTC.
For the married couple,
1. correctly identify their genotypes,
2. complete a Punnett square showing the expected offspring of the couple, and
3. identify the genotypic and phenotypic ratios of their offspring
Are Mendel’s principles of segregation and independent assortment even relevant today in the age of genomics, when it is possible to sequence an organism’s entire genome and determine all of its genetic information? Why is it important to study these principles, and how can they be used?
Chapter 25 Solutions
Concepts of Genetics (12th Edition)
Ch. 25 - A homozygous plant with 20-cm-diameter flowers is...Ch. 25 - The following table shows measurements for fiber...Ch. 25 - The following cable gives the percentage of twin...Ch. 25 - At an interview with a genetic counselor, a couple...Ch. 25 - Prob. 2CSCh. 25 - At an interview with a genetic counselor, a couple...Ch. 25 - HOW DO WE KNOW? In this chapter, we focused on a...Ch. 25 - CONCEPT QUESTION Review the Chapter Concepts list...Ch. 25 - Define the following: (a) polygenic, (b) additive...Ch. 25 - A dark-red strain and a white strain of wheat are...
Ch. 25 - Height in humans depends on the additive action of...Ch. 25 - An inbred strain of plants has a mean height of 24...Ch. 25 - Erma and Harvey were a compatible barnyard pair,...Ch. 25 - In the following table, average differences of...Ch. 25 - What kind of heritability estimates (broad sense...Ch. 25 - List as many human traits as you can that are...Ch. 25 - Corn plants from a test plot are measured, and the...Ch. 25 - The following variances were calculated for two...Ch. 25 - The mean and variance of plant height of two...Ch. 25 - Prob. 14PDQCh. 25 - Prob. 15PDQCh. 25 - In an assessment of learning in Drosophila, flies...Ch. 25 - Prob. 17PDQCh. 25 - Prob. 18PDQCh. 25 - In a population of 100 inbred, genotypically...Ch. 25 - Many traits of economic or medical significance...Ch. 25 - A 3-inch plant was crossed with a 15-inch plant,...Ch. 25 - In a cross between a strain of large guinea pigs...Ch. 25 - Type A1B brachydactyly (short middle phalanges) is...Ch. 25 - In a series of crosses between two true-breeding...Ch. 25 - Students in a genetics laboratory began an...Ch. 25 - Prob. 26ESPCh. 25 - Canine hip dysplasia is a quantitative trait that...Ch. 25 - Floral traits in plants often play key roles in...Ch. 25 - In 1988, Horst Wilkens investigated blind...
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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?arrow_forwardPedigree 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?arrow_forwardPedigree 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?arrow_forward
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