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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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 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_forwardConnection to Quantitative traits: SNPs are inherited in a Mendelian fashion and are often polygenic in nature. We can think of SNPs in terms of either contributing or non-contributing alleles. A study of SNPs correlated with heart disease has shown that heart problems are severe if 9 or more of the alleles at 6 loci are of the contributing variety. What is the probability the following parents will have a child that is susceptible heart disease? AaBbccDDEEFf x AaBbCCDdEeffarrow_forward
- If the chi-square value came out to 14,224.221 and the p-value was said to be less than 0.01, what do you conclude about whether these traits follow a simple Mendelian inheritance pattern? Explain your answer.arrow_forwardHow can we explain the striking contrast in the number of major genes underlying quantitative traits between domesticated animals (where only a few QTLs are typically involved) and humans (where the QTLs for manytraits number in the hundreds)?arrow_forwardIf the heritability of a human trait is .50 at age six, what would you expect it to be at age 20?arrow_forward
- Aside from the Punnett square, are there other ways to understand the inheritance of traits in humans, animals and/or plants? Give at least one and describe if there is.arrow_forwardIf the frequency of those exhibiting a monogenic autosomal recessive phenotype caused by a rare clinically relevant allele is 1/8500 in a given population, what is the carrier frequency? Please give your answer as a percentage to 3 decimal places, do not include the % symbol. ANSWER: In a population where the frequency of those exhibiting a monogenic autosomal recessive phenotype caused by only one known mutation is 1/8500 the carrier frequency is a percent.arrow_forwardWhat is the difference between a Mendelian multifactorial trait and a polygenic multifactorial trait?arrow_forward
- What is a Mendelian population? How is the gene pool of a Mendelian population usually described?arrow_forwardIn the genetics unit you learned that sickle cell anemia is an autosomal recessive condition. In 2016, assume in the City of Markham there are 1000 people out of 300000 people who have sickle cell anemia. Assume global warming continues for the next 50 years and in the year 2066 there are 20000 people out of 500000 in Markham who have sickle cell anemia. a)What are the allele frequencies in 2016? What are the allele frequencies in 2066? Is microevolution evident? b)Due to global warming, assume the numbers of malaria carrying mosquitoes in Markham dramatically increased between 2016 and 2066. What do you believe is the main cause of the microevolution in Markham? (Hint- refer to the 5 factors affecting microevolution and refer back…arrow_forwardA study of SNPs associated with familial hypercholesterolemia has revealed that 7 or more contributing alleles at 6 loci can lead to elevated levels of cholesterol in the blood. What is the probability that the following parents, AaBbccDDeeFF x AAbbCCDdEeFF, will have children that are susceptible to hypercholesterolemia?arrow_forward
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