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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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]?
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
Suppose 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.
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_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 (%) Characteristic Monozygotic Dizygotic Migraine headaches 60 30 Eye color 100 40 Measles 90 90 Club foot 30 10 High blood pressure 70 40 Handedness 70 70 Tuberculosis 5 5arrow_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_forward
- In 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_forwardTwo 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_forwardList 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_forward
- If 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_forwardUsing 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_forwardIndividuals who find the taste of cilantro to be pleasent have a domiant allele for this taste sensation. Individuals who do not like this flavor are recessive. for this particular taste sensation. A parent who does not like Cilantro has a child with someone who is homozygous dominant for liking the flavor of Cilantro. What are the chances that teh child will not like the Cilantro? a) 25% b) 50% c) 0% d)100%arrow_forward
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