Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN: 9781305251052
Author: Michael Cummings
Publisher: Cengage Learning
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Chapter 5, Problem 17QP
Monozygotic (MZ) twins have a concordance value of 44% for a specific trait, whereas dizygotic twins have a concordance value of less than 5% for the same trait. What could explain why the value for MZ twins is significantly less than 100%?
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Assume that the concordance value for a particular trait is 85% for both monozygotic and dizygotic twins.
What can be concluded about this trait?
○ It is caused by environmental factors in dizygotic twins but by genetic factors in monozygotic twins.
It is likely caused almost exclusively by genetic factors.
It is caused by both genetic factors and environmental factors.
It is likely caused almost exclusively by environmental factors.
It is caused by genetic factors in dizygotic twins but by environmental factors in monozygotic twins.
Incorrect
There are two types of alleles:
Type B1 and Type B2
(In total there are 10)
Type B1 has 6
Type B2 has 4
Question:
What is the probability of an individual in the offspring generation being homozygous [p^2] for B1?
What is the probability of an individual in the offspring generation being homozygous [q^2] for B2?
What is the probability of an individual in the offspring gen being heterozygous[2pq]?
Many researchers have estimated the heritability of human traits by comparing the correlation coefficients of monozygotic and dizygotic twins (see pp. 731–732). One of the assumptions made in using this method is that monozygotic twin pairs experience environments that are no more similar to each other than those experienced by dizygotic twin pairs. How might this assumption be violated? Give some specific examples of how the environments of two monozygotic twins might be more similar than the environments of two dizygotic twins.
Chapter 5 Solutions
Human Heredity: Principles and Issues (MindTap Course List)
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- A pedigree analysis was performed on the family of a man with schizophrenia. Based on the known concordance statistics, would his MZ twin be at high risk for the disease? Would the twins risk decrease if he were raised in an environment different from that of his schizophrenic brother?arrow_forwardSuppose that a geneticist studies a series of characteristics in monozygotic twins and dizygotic twins. He finds various rates of phenotypic concordance for the characteristics, as shown in the table. Rate of phenotypic concordance (%) Characteristic Monozygotic Dizygotic migraine headache 60 30 eye color 100 40 measles 90 90 clubfoot 30 10 high blood pressure 70 40 handedness 70 70 tuberculosis Classify each characteristic according to whether the corresponding rates of concordance indicate a genetic influence, an environmental influence, or both genetic and environmental influences.arrow_forwardA geneticist studies a series of characteristics in pairs of monozygotic and dizygotic twins, obtaining the concordances listed below. For each characteristic, indicate whether these concordances suggest genetic influences, environmental influences, or both. Explain your reasoning. Concordance (%) Dizygotic Characteristic Monozygotic Migraine headaches 60 30 Eye color 100 40 Measles 90 90 Club foot 30 10 High blood pressure 70 40 Handedness 70 70 Tuberculosisarrow_forward
- Two strains of corn are 1 m (100 cm) and 3.4 m (340 cm) tall. Assume the difference arises from alleles at four genes, each with two alleles, with one allele of each gene contributing additively to height. The 3.4-m plant's genotype is AABBCCDD and the 1-m plant is aabbccdd. Part 1 How many centimeters of height does each allele that is represented by a capital letter contribute? 1.7 cm 30 cm 42.5 cm 60 cm 120 cm Part 2 What would be the shortest plants produced from the following cross? AaBBccDd× AabbccDd 100 cm 120 cm 130 cm 160 cm 175 cmarrow_forwardIf one human parent is heterozygous for blood type A (IAi), and the second parent is heterozygous for blood type B (IBi), what are the expected phenotypic ratios in their children? a. 1/4 with blood type AB, 1/4 with blood type A, 1/4 with blood type B, and 1/4 with blood type O b. 1/4 with blood type A (IAi), 1/2 with blood type AB (IAIB), and 1/4 with blood type B (IBi) c. 1/2 with blood type AB (IAIB), and 1/2 with blood type O (ii) d. 1/2 with blood type A (IAi), and 1/2 with blood type B (IBi) e. 1/2 with blood type A (IAi), and 1/2 with blood type O (ii)arrow_forwardIn humans the absence of a cleft chin is dominant to the presence of a cleft chin. Two individuals, both of whom are heterozygous for a recessive allele that causes the cleft chin phenotype have 5 children, what is the probability that 3 of their children would not have a cleft chin and 2 would have a cleft chin? 0.0037 0.026 0.237 0.264arrow_forward
- List any phenotypes (e.g., physical or behavioral) that might differ between the average person who is a twin and the average person who is a singleton. Explain your answer (provide an external source, if possible). For most phenotypes, are twins representative of the general population? Why or why not? Do you think the experience of being an MZ twin is very different from being a DZ twin? In which ways?arrow_forwardThe incidence of a rare autosomal recessive genetic disorder, Tay-Sachs, is approximately 1 in 3,500 in a certain population. Assuming that this population is in Hardy- Weinberg equilibrium, what is the probability that a phenotypically normal female with no family history, and a phenotypically normal male who had an affected great- aunt, will have a child who is a carrier for Tay-Sachs? O 1.96% O 9.99% O 0.28% O 0.03% O 2.2% O 0.14%arrow_forwardIf monozygotic twins show complete concordance for a trait, whether they are reared together or apart, what does this suggest about the heritability of the trait?arrow_forward
- Using the HardyWeinberg Law in Human Genetics Suppose you are monitoring the allelic and genotypic frequencies of the MN blood group locus (see Question 2 for a description of the MN blood group) in a small human population. You find that for 1-year-old children, the genotypic frequencies are MM = 0.25, MN = 0.5, and NN = 0.25, whereas the genotypic frequencies for adults are MM = 0.3, MN = 0.4, and NN = 0.3. a. Compute the M and N allele frequencies for 1-year-olds and adults. b. Are the allele frequencies in equilibrium in this population? c. Are the genotypic frequencies in equilibrium?arrow_forwardIn a hypothetical population of 2500 people, 2275 people have brown eyes and 225 people have blue eyes (the homozygous-recessive phenotype). If there are 4000 children produced by this generation, how many (i.e., what number) of the children would be expected to be heterozygous for eye color?arrow_forwardWhat are the possible phenotypic (P) and genotypic (G) ratios if you cross two parents who are carriers of dominant traits following Mendelian laws of heredity? P: 2:1; G: 3:1 P: 1:2:1; G: 1:3 P: 3:1; G: 1:2:1 P: 3:1; G: 2:1:1arrow_forward
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