Chapter 20, Problem 1U

Assortative mating

a. affects genotype frequencies expected under Hardy–Weinberg equilibrium.

b. affects allele frequencies expected under Hardy–Weinberg equilibrium.

c. has no effect on the genotypic frequencies expected under Hardy–Weinberg equilibrium because it does not affect the relative proportion of alleles in a population.

d. increases the frequency of heterozygous individuals above Hardy–Weinberg expectations.

Summary Introduction

Introduction:

Assortive mating involves matting of phenotypically similar individuals. It is a type of non-random mating those results in the frequencies of particular genotypes and the allelic frequency of that population is different from the Hardy–Weinberg principle.

Answer to Problem 1U

Correct answer:

Assortive mating occurs when individuals choose their mates based on their resemblance each other on the basis of certain phenotype that upset the Hardy–Weinberg principle. Therefore option a. is correct.

Explanation of Solution

Reason for the correct statement:

Assortive matting involves mates of similar phenotype. Its effect is limited to genes that influence the phenotype and its impact on the overall population is limited by mating that is otherwise random.

Option a. is given as “affects genotype frequencies expected under Hardy–Weinberg equilibrium”.

As, the random mating is a requirement of genetic equilibrium whereas assortive mating affects the genotypic frequency within individuals as it select the mate based on similar traits and does not support the Hardy–Weinberg principle for genetic equilibrium.

Hence, the option a is correct.

Reasons for incorrect statements:

Option b. is given as “affects allele frequencies expected under Hardy–Weinberg equilibrium”.

Assortive mating affects the genotypic frequency not the allelic frequency as expected under Hardy-Weinberg equilibrium. So it is a wrong answer.

Option c. is given as “has no effect on the genotypic frequencies expected under Hardy–Weinberg equilibrium because it does not affect the relative proportion of alleles in a population”.

Assortive mating occurs between the individual of similar traits it affects the genotypic frequency and not the allelic frequency in a population as expected under Hardy-Weinberg equilibrium. So it is a wrong answer.

Option d. is given as “increases the frequency of heterozygous individuals above Hardy–Weinberg expectations”.

Assortative mating results when individuals mate with partners that are like themselves in certain phenotypic characters, it results in fewer heterozygotes than Hardy-Weinberg predicts. So it is a wrong answer.

Hence options b, c, and d are incorrect.

Conclusion

Assortative mating affects genotype frequencies expected under Hardy–Weinberg equilibrium.