Essentials of Genetics (9th Edition) - Standalone book
9th Edition
ISBN: 9780134047799
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 21, Problem 22PDQ
While most quantitative traits display continuous variation, there are others referred to as “threshold traits” that are distinguished by having a small number of discrete
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Which of the following best explains how individuals who inherit phenylketonuria alleles can avoid the symptoms of this disease (mental impairment, foul smelling urine)?
It exhibits variable expressivity.
The expression of this disease depends on the environment. If the individual removes phenylalanine from their diet they can avoid the disease entirely.
PKU alleles are epistatic to alleles of another gene, which acts downstream in phenylalanine metabolism.
These individuals supplement their diets with enzymes that break-down phenylalanine.
Huntington disease (HD) is a rare dominant condition in humans that results in a slow but inexorable deterioration of the nervous system. HD shows what might be called “age-dependent penetrance,” which is to say that the probability that a person with the HD genotype will express the phenotype varies with age. Assume that 50% of those inheriting the HD allele will express the symptoms by age 40. Susan is a 35-year-old woman whose father has HD. She currently shows no symptoms. What is the probability that Susan will show symptoms in five years?
Epistasis refers to the interaction of genes wherein the expression of one gene is dependent on another gene. For example, suppose there are two genes that code for flower color in a plant, where red, WW or Ww, is typically dominant over expression of white, ww, and yellow, YY or Yy, is typically dominant over green, yy. One type of epistasis expresses a pattern where a dominant allele in either gene produces a red phenotype.
Classify the F1 flower color ratio that would be produced from the dihybrid cross for each type of epistasis.
Chapter 21 Solutions
Essentials of Genetics (9th Edition) - Standalone book
Ch. 21 -
CASE STUDY | A genetic flip of the coin
On July...Ch. 21 - CASE STUDY|A genetic flip of the coin On July 11,...Ch. 21 -
CASE STUDY|A genetic flip of the coin
On July...Ch. 21 - HOW DO WE KNOW?
1. In this chapter, we focused on...Ch. 21 - Review the Chapter Concepts list on page 422....Ch. 21 -
3. Define the following: (a) polygenic, (b)...Ch. 21 - A dark-red strain and a white strain of wheat are...Ch. 21 - Height in humans depends on the additive action of...Ch. 21 -
6. An inbred strain of plants has a mean height...Ch. 21 - Prob. 7PDQ
Ch. 21 - In the following table, average differences of...Ch. 21 - What kind of heritability estimates (broad sense...Ch. 21 - List as many human traits as you can that are...Ch. 21 - Corn plants from a test plot are measured, and the...Ch. 21 -
12. The following variances were calculated for...Ch. 21 - The mean and variance of plant height of two...Ch. 21 - A hypothetical study investigated the vitamin A...Ch. 21 - In a herd of dairy cows the narrow-sense...Ch. 21 - In an assessment of learning in Drosophila, flies...Ch. 21 - Suppose you want to develop a population of...Ch. 21 -
18. In a population of tomato plants, mean fruit...Ch. 21 - In a population of 100 inbred, genotypically...Ch. 21 - In a cross between a strain of large guinea pigs...Ch. 21 - While most quantitative traits display continuous...
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- Total fingerprint ridge count exemplifies a polygenic inheritance pattern. Penrose (1969) and others have suggested that a minimum of seven gene loci contribute to TRC, but a four-locus model is hypothesized in the problems that follow. Thus, AABBCCDD represents the genotype for maximum ridge count and aabbccdd symbolizes the genotype for the minimum ridge count. Assume that each active allele adds 15 ridges to the TRC of the male and 12 to the TRC of the female and that having the genotype aabbccdd produces a baseline TRC of 70 for males and 50 for females. Predict the TRC for each of the following individuals: Genotype Male Female AABBCCDD AabbccDd AaBBCcDD aaBbCCDdarrow_forwardTotal fingerprint ridge count exemplifies a polygenic inheritance pattern. Penrose (1969) and others have suggested that a minimum of seven gene loci contribute to TRC, but a four-locus model is hypothesized in the problems that follow. Thus, AABBCCDD represents the genotype for maximum ridge count and aabbccdd symbolizes the genotype for the minimum ridge count. Assume that each active allele adds 15 ridges to the TRC of the male and 12 to the TRC of the female and that having the genotype aabbccdd produces a baseline TRC of 70 for males and 50 for females. Predict the TRC for each of the following individuals: Genotype Male Female AABBCCDD AabbccDd AaBBCcDD aaBbCCDd A. Write the genotypes of parents who are heterozygous for all four genes. B. Write the genotype of their child who has the maximum number of active alleles possible. C. What are the TRCs for the parents? D. What is the TRC of the child from B (assume male)?…arrow_forwardIn humans, four different blood types (A, B, AB, and O) are encoded by three alleles 1, 1, and i Individuals with both I and I alleles have blood type AB (red blood cells with both A and B antigens). Two copies of the i allele are required for an individual to have blood type O (red blood cells with no antigens). Which of the following correctly indicates the relationship between the I and / alleles for the blood type gene? Select one: OA. I is dominant to / OB. I is recessive to i OC. I and I are co-dominant OD. I and/exemplify incomplete dominancearrow_forward
- Consider the MN blood system in humans. This blood system consists of only two alleles, M and N, and they are codominant to each other. Three genotypes are possible, and these genotypes can be easily identified through simple blood typing procedures, including the heterozygous MN due to the codominant mode of inheritance. Consider the following data: Phenotype Genotype Number of individuals M MM 89 MN MN 162 N NN 79 1. How many alleles exist in this population? 2. What is the genotypic frequency of the M blood type in the population? 3. What is the allelic frequency of M? 4. What is the allelic frequency of N? 5. What is the genotypic frequency of MN? Write your answers directly. You do not need to show your solution.arrow_forwardAPOE gene has been found to be a major contributor to sporadic Alzheimer's disease (AD), by acting as an age-of-onset modifier for the common relatively late-onset forms of the disease. Among four alleles causing early onset of AD, the epsilon4 allele (APOE4) disrupts this function. If you generate transgenic monkeys in which the normal allele of APOE gene is knocked out, what phenotype will you expect for those knockout monkeys? A. The APE mRNA expression will be completely suppressed. B. They slow down the development of AD. C. They develop AD early. D. They don't show any AD symptom.arrow_forwardSome heterozygotes express a phenotype that is intermediate between the dominant and recessive phenotype. For example, in 4 o’clock flowers the gene for red pigmentation is dominant and the gene for white pigmentation is recessive. However, heterozygotes are pink. The dominant allele does not completely mask expression of the recessive allele: it is incompletely dominant. a. By observing flower color in 4 o’clock flowers, is it possible to unambiguously determine the genotype? YES/NO. Explain your answer. b. Is the same true for flower color in snow peas? YES/NO Why or why not?arrow_forward
- Why are genetic variants with large effects on traits generally rarer than those with smaller effects? Explain how this relates to the observation that the heritability of common diseases is driven by common variantsarrow_forwardQTL mapping and GWA (association) mapping are two different methods used to identify genes that affect complex traits. For each of the following statements, choosewhether it applies to QTL mapping, association mapping, or both.whether it applies to QTL mapping, association mapping, or both.arrow_forwardA dominant genetic factor P is required for the formation of an enzyme needed to convert phenylalanine to tyrosine. The recessive allele “p” result in lack of the enzyme and as a consequence phenylketonuria (PKU) can ensure. A woman who was spared the dire effect of PKU as a result of a special diet during infancy and childhood is married to a man who does not have PKU but does carry the recessive allele. During her pregnancy the woman is placed on a special diet once more, since excess phenylalanine and other toxic product can cross the placenta in a PKU women and resulted in mental retardation in the new born. What geneotype are to be expected among the off spring in this case and what would be their phenotype?arrow_forward
- The following genetic map describes three hypothetical human autosomal genes, each of which exhibits two alleles. Two-factor map distances are shown. A = Artistic (dominant) a = Inartistic (recessive) M = Moral (dominant) m = Immoral (recessive) G = Generous (dominant) g = Greedy (recessive) Assume that these traits exhibit simple Mendelian dominance/recessiveness. The coefficient of coincidence for this map is 0.4. An artistic, moral, generous heterozygous female of genotype AMG/amg marries an inartistic, immoral, greedy homozygous male of genotype amg/amg. What is the probability that their firstborn child will be inartistic, immoral and greedy? What is the probability that their firstborn child will be inartistic, moral and generous? What is the probability that their firstborn child will be artistic, immoral and generous?arrow_forwardSuppose a geneticist is using a three-point test cross to map three linked rabbit morphology and behavioral mutations called si, It, and Le. The gene si is associated with the silky fur phenotype, and It is associated with the long-tailed phenotype. Both si and It are recessive mutations with respect to wild type. Le is a dominant mutation that confers the lethargic phenotype. The geneticist first crosses true-breeding lethargic rabbits to true-breeding silky fur, long-tailed rabbits. Next, the geneticist backcrosses the Fj progeny to the silky fur, long-tailed parents, and obtains the results reported in the table. Phenotype Number lethargic 815 silky fur, long-tailed 807 long-tailed 177 silky fur, lethargic 179 silky fur 7 long-tailed, lethargic 5 silky fur, long-tailed, lethargic 29 wild type 29 Place the genes in the correct order in the chromosome. Answer Bank si It Learrow_forwardMarfan syndrome is a disease caused by a rare dominant allele of the fibrillin-1 gene. Fibrillin-1 is an important component of the extracellular matrix, and people with the disease-causing allele have abnormal connective tissue. An affected mother (Marta) and an unaffected father (Joe) have one unaffected daughter (Luisa - she does not exhibit any traits of the syndrome). If Luisa has a child with Nico (unaffected), what is the probability that her child will inherit Marfan syndrome? Select one: a. 50% b. 25% c. 100% d. 0% e. 75%arrow_forward
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