Question

A large population of zebrafish has been allowed to breed randomly for a number of generations in a laboratory.
After ten generations, 25% of the fish display a recessive genotype (dd), the same percentage as at the beginning of the breeding program. The rest of the fish show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What is the most reasonable explanation of the fact that the frequency of the recessive genotype (dd) at generation ten is the same as the frequency of the recessive genotype (dd) at generation one?

• A. Sexual selection occurred that favoured allele d
• B. The genotype DD is lethal
• C. The population is undergoing genetic drift
• D. The two phenotypes are equally adaptive under laboratory conditions

Answer 1

The correct option is D The two phenotypes are equally adaptive under laboratory conditions

Since, the gene frequencies have remained constant through out the experimental period, that is the recessive and dominant frequency did not alter. So, they exhibit a similar kind of adaptation.

So, the correct answer is 'The two phenotypes are equally adaptive under laboratory conditions'