Chapter 21, Problem 1TYK

The reason spontaneous mutations do not have an immediate effect on allele frequencies in a large population is that:

a. mutations are random events, and mutations may be eitherbeneficial or harmful.

b. mutations usually occur in males and have little effect oneggs.

c. many mutations exert their effects after an organism hasstopped reproducing.

d. mutations are so rare that mutated alleles are greatlyoutnumbered by nonmutated alleles.

e. most mutations do not change the amino acid sequence of aprotein.

Summary Introduction

Introduction:

Mutations are the changes that occur at the gene level, which includes the insertion, substitution, and replacement of one of the nucleotides in the DNA sequences. These changes are heritable if it occurs in germ cells. Mutations can be deleterious, lethal and neutral, based upon their effects on the gene pool.

Answer to Problem 1TYK

Correct answer:

Mutations are so rare that mutated alleles are greatly outnumbered by nonmutated alleles.

Explanation of Solution

Justification/ Explanation for the correct answer:

Option (d) states that mutations are so rare that mutated alleles are greatly outnumbered by nonmutilated alleles. New mutations are not that frequent and show no or minimal effect on the allelic frequency in large populations. Mutation happens very rarely, one in millions of the gametes. This results in the outnumbering of the mutated alleles by the nonmutated alleles. Hence, option (d) is the correct answer.

Explanation for the incorrect answers:

Option (a) states that mutations are random events which may be either beneficial or harmful. Mutations occur spontaneously, and most of the mutations are not beneficial while there are some mutations which show neutral effects. Mutation can also be beneficial, which are called advantageous mutations. But these events can effect the allele frequency. So, it is an incorrect option.

Option (b) states that mutation usually occurs in male and have little effect on eggs. The mutation occurs in the germ cells of both male and female organisms. It can be lethal, as well as, neutral mutation and can also affect the allele frequency. So, it is an incorrect option.

Option (c) states that many mutations exert their effects after the organism has stopped reproducing. The mutations are heritable and can be passed on to the next generation through reproduction. If the organism stops reproducing, the mutated allele will increase and can affect the allele frequency. So, it is an incorrect option.

Option (e) states that most mutation does not change the amino acid sequence of a protein. The mutations in the third nucleotide codon of an amino acid do not change the protein expression. These mutations show fewer effects on the allele frequency. This is not the reason for the immediate effect on allele frequencies. So, it is an incorrect option.

Hence, options (a), (b), (c), and (e) are incorrect.

Conclusion

It can be concluded that mutations can be spontaneous and occur rarely. These mutations do not affect the allele frequencies of a large group of the population, under as the nonmutated alleles are large in number in comparison to mutated alleles.