Question

In fruit flies, dumpy wings are shorter and broader than normal wings. The allele for normal wings [D] is dominant to the allele for dumpy wings [d]. Seventy five normal-winged and twenty five dumpy-winged flies. The genotype of parents would be.
(A) DD and DD
(B) DD and Dd
(C) Dd and Dd
(D) Dd and dd

Answer 1

Hint: The dominant D allele in fruit flies results in extended wings, whereas the recessive D allele results in vestigial wings. Fly genotypes DD or Dd will have extended wings, while genotype dd will have rudimentary wings.

Complete Step by Step Answer:
Seventy five normal-winged fruit flies are produced and seventy five dumpy-winged fruit flies are produced, so the phenotypic ratio is 3:1. Those seventy five fruit flies can have a genotype of DD or Dd and twenty five will surely have genotype of dd.

Suppose if parents will have genotype DD and DD then such progeny is not possible, so option (A) is incorrect. If parents will have genotype DD and Dd then progeny will be DD and Dd, so option (B) is also incorrect. If parents will have genotype of Dd and dd then progeny will have genotype of Dd and dd, so option (D) is also incorrect. Now, if parents will have genotype of Dd and Dd then progeny will be DD, Dd and dd that is the genotypic ratio can be 1:2:1 and phenotypic ratio will be 3:1. So, option (C) is correct.

By cross:
Gametes produced by Mother - D and d
Gametes produced by Father - D and d

Parental Gametes	D	d
D	DD	Dd
d	Dd	dd

The offspring produced are - 1 DD : 2 Dd : 1 dd
Genotypic ratio: 1:2:1
Phenotypic ratio: 3:1
So, option (C) is correct answer.



Note: Fruit flies of the wild variety have flat, straight wings. You can infer that this is the best wing form for flying based on the fact that this is a highly typical insect wing shape. But occasionally, fruit flies are born with incredibly tiny wings.