6. To quantify the total phenotypic variance (V P ) for a polygenic trait such a

Question

6. To quantify the total phenotypic variance (VP) for a polygenic trait such as body height, it is necessary to have data on:

            a. the difference in height among individuals who have the same genotype

            b. the height of a large sample of individuals from the population

            c. the frequency of alleles at loci that influence body height

            d. the phenotypic effect of an allele substitution (a)

            e. both (c) and (d)

7. Brain size and body size in mice are known to be genetically correlated because:

a. genes affecting both traits have been found to be linked together on the same chromosome

b. parents with greater than average body size tend to have offspring with lower than average brain size

c. resources that are devoted to body development tend to limit what's available for brain development

d. artificial selection on one trait causes the other to change as well

e. there is no fitness benefit to having a large brain unless body size increases as well

8. Consider a population with two loci (A, B), each with two alleles (A, a; B, b). What are the haplotype frequencies in this population if the allele frequencies are A = 0.5, a = 0.5, B = 0.7, b = 0.3?

a. AB = 0.35, Ab = 0.15,       aB = 0.35,        ab = 0.15

b. AB = 0.45, Ab = 0.05,       aB = 0.25,        ab = 0.25

c. AB = 0.4,     Ab = 0.1,         aB = 0.3,          ab = 0.2

d. AB = 0.125, Ab = 0.25,       aB = 0.25,        ab = 0.125

e. Cannot be determined based on the information provided

9. One major way that gametic disequilibrium (linkage disequilibrium) is reduced is:

a. antagonistic selection where two different selective agents are acting that have opposite effects on fitness

b. genetic drift leading to the accumulation of certain allele combinations

c. inbreeding

d. crossing over during meiosis in double heterozygotes

e. natural selection acting at the gamete stage (gametic selection)

10. When stabilizing selection acts on a polygenic trait, the immediate effect is to:

a. reduce the phenotypic effect of an allele substitution (a)

b. reduce the realized heritability (h2R)

c. increase the environmental variance (VE)

d. reduce the phenotypic variance (VP)

e. increase the genetic variance (VG)

11. Regarding the Bailey & Pillard study of sexual orientation in twins, an essay by Byrd, Cox and Robinson (2001) posted on the NARTH website pointed out that the concordance of homosexuality in identical twins is only 52%. The essay then claims that this proves that genes do not influence sexual orientation, saying "If homosexuality were in the genetic code, all of the identical twins would have been homosexual."   This argument is equivalent to which of these claims:

a. a trait cannot be heritable if VG > VE

b. the fact that VE is greater than zero implies that VG = 0

c. in a large sample of multiple pairs of identical twins, VP = VG

d. if two members of an identical twin pair were raised in different families, this would have no influence on the concordance value for sexual orientation

e. if non-identical twins were also found to have a concordance value 52% for sexual orientation, this would prove that homosexuality was heritable.

12. Listed below are four evolutionary explanations for disease. Which one best describes the antagonistic pleiotropy hypothesis for aging?

a. Natural selection has not had time to catch up with environmental changes.

b. Natural selection favors reproductive success, even at the expense of vulnerability to disease.

c. Some disease symptoms, though unpleasant, are actually beneficial.

d. Natural selection lacks foresight; we are stuck with historically contingent relics of the past.

Explanation / Answer

6)

The VP (total phenotypic variance) = VG (genetic variance) + VE (environmental variance). Therefore, to quantify the total phenotypic variance (VP) for a polygenic trait such as body height, it is necessary to have data on:

Thus, the correct option is (e) both (c) and (d).

7)

Brain size and body size in mice are known to be genetically correlated because artificial selection on one trait causes the other to change as well. Thus, the correct option is (D).

8)

The allele frequencies are:

Thus,

f(AB) = (0.50.7) = 0.35

Thus, the correct option is (a).

9)

Linkage disequilibrium is reduced crossing over during meiosis in double heterozygotes. Thus, the correct option is (d).

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