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Exam 17: Quantitative Genetics

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Question 21

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Suppose that researchers estimate that broad-sense heritability of IQ in Sweden is 0.8.Which of the following conclusions is valid, assuming that the estimate is accurate?

A) Most variance for IQ in Sweden is due to total genetic variance.
B) In Sweden, the environment does not play a large role in determining the IQ of individuals.
C) Enriching the environment of poor children in Sweden would not lead to a big improvement on IQ tests.
D) Broad-sense heritability of IQ in the United States probably is close to 0.8.
E) If another country has a lower broad-sense heritability for IQ, then this difference must be genetically based.

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Question 22

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In wheat, kernel color is determined by additive alleles at two unlinked loci.If two plants, one with dark red kernels (+++- genotype) , and one with light red kernels (+- - - genotype) , are crossed, what fraction of the offspring is expected to have phenotypes distinct from parental colors?

A) 1/4
B) 4/16
C) 6/16
D) 1/2
E) 10/16

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Question 23

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The following broad-sense heritability values were estimated for four different traits: 0.2, 0.3, 0.4, and 0.5 for traits A, B, C, and D, respectively.Which of these traits experiences the LARGEST influence of the environment?

Estimates of heritability made by comparing related individuals assume that the environments of related individuals:

In wheat, kernel color is determined by additive alleles at two unlinked loci.If two plants, with red kernels, heterozygous at both loci, are crossed, what fraction of the offspring is expected to have phenotypes distinct from parental?

Which of the following traits is NOT a continuous trait?

Flower diameter in sunflowers is a quantitative trait.A plant with 6-cm flowers, from a highly inbred strain, is crossed to a plant with 30-cm flowers, also from a highly inbred strain.The F₁ have 18-cm flowers.F₁ × F₁ crosses yield F₂ plants with flowers ranging from 6 to 30 cm in diameter, in approximately 4-cm intervals (6, 10, 14, 18, 22, 26, 30) . An 18-cm F₁ plant is crossed to a 6-cm plant.What is the probability of an offspring with one additive allele, if all genes that influence this trait are unlinked?

Cloning is a procedure by which exact genetic duplicates are made.A litter of cloned rabbits was born from a single surrogate mother rabbit.Despite being genetically identical, each of the baby rabbits looked very different from one another.Explain in detail why this might have occurred.

The following components of the total phenotypic variance were estimated at three agriculturally important traits in corn. Determine which of these traits will have the BEST response to selective breeding.

Knowing the _____ of a trait has great practical importance because it allows statistical predictions regarding the phenotypes of offspring to be made on the basis of the parents' phenotypes.

Total phenotypic variance can be broken down into all but one of which of the following components?

A certain disease phenotype is a threshold trait, where disease occurs only if the number of susceptibility alleles in a genotype exceeds 3.How many phenotypic categories can be observed if the number of quantitative susceptibility loci has been determined as 5?

_____ measures the effect of alleles at a locus interacting in a non-additive fashion.

Recently, genome-wide association studies that locate genes influencing quantitative traits have been facilitated by the use of:

Which of the following traits is a meristic trait?

A study was conducted to investigate the levels of calcium and growth hormone excreted in chicken dung on a major chicken farm.The variances (V)were calculated and are shown below. a.Calculate the narrow-sense heritability for both traits (calcium and growth hormone levels). b.Which trait, if any, will most likely respond to artificial selection?

The height of a type of bean plant is determined by five unlinked genes called A, B, C, D, and E.Each gene has two alleles: additive (uppercase letter)and nonadditive (lowercase letter).The shortest plants are 130 cm.The tallest plants are 220 cm. a.Estimate how many centimeters each allele contributes to the height difference of 90 cm. b.The genotypes are known for two bean plants.Plant 1 is genotype AABbccDdEE.Plant 2 is genotype aaBBCcDdEE.What are their heights? c.If the two plants in the previous question are crossed, could they produce a plant that is taller than either parent? How? d.All the genes are unlinked.Determine the probability of an AbcdE gamete from plant 1, and an aBcdE gamete from plant 2.What will be the genotype and phenotype of a plant from these gametes, and what is the probability of a plant with this genotype? e.If the progeny plant from the cross in the previous question was only 60 cm because of an allele in a gene other than A-E, what genetic phenomena are at work? f.If the progeny plant with the genotype in part (d)was a few centimeters taller than your prediction, how would you explain it?

The following narrow-sense heritability values were estimated for four different traits: 0.2, 0.3, 0.4, and 0.5 for traits A, B, C, and D, respectively.Which of these traits has the LARGEST dominance genetic variance?

When _____ is high for a particular trait, offspring tend to resemble their parents for that trait.

All of the following statements about heritability are true EXCEPT: