Kaplan Nursing Entrance Practice Exam

If a homozygous dominant male fruit fly is crossed with a female fruit fly with vestigial wings, what percentage of their female progeny will have wild-type wings?

1. 50%

2. 25%

3. 100%

4. 75%

The correct answer is: 100%

To understand why the answer is 100%, let's first clarify the genetic traits involved in this question. The male fruit fly is homozygous dominant for the wild-type wings, which means it carries two dominant alleles for normal wing development. The female fruit fly has vestigial wings, indicating she carries two recessive alleles for this trait, as vestigial wings are the result of a recessive genetic condition. When these two individuals are crossed, all of their progeny will inherit one allele from the male (the dominant allele for wild-type wings) and one allele from the female (the recessive allele for vestigial wings). Since the male is homozygous dominant, all the offspring will receive a dominant allele for wings from him. Consequently, all female progeny produced from this cross will express the dominant phenotype of wild-type wings, as the dominant allele completely masks the effect of the recessive allele received from the mother. Therefore, 100% of the female progeny will exhibit wild-type wings. This understanding is essential in genetics, as it highlights the principles of dominance and genotype interactions when examining inheritance patterns.