Question

In the Australian sheep blowfly an autosomal gene yellow (alleles y, y + ) determines the recessive phenotype yellow eyes. A pure breeding strain with yellow eyes is crossed to a pure breeding wild-type strain. The F1 flies from this cross are allowed to interbreed to produce the F2 generation.

41 The phenotype of the F1 flies will be

A. wild type B. yellow eyes C. recessive D. y + y

42 The F1 flies are testcrossed, the phenotypic ratio of the offspring of the testcross is expected to be

A. 1 wild-type : 1 yellow eye B. 3 wild-type : 1 yellow eye C. 3 yellow eye : 1 wild-type D. 9 wild-type : 7 yellow eye

A second autosomal gene topaz (alleles t, t + ) determines a recessive yellow eye phenotype identical to that of yellow. The topaz gene assorts independently from the yellow gene.

43 A pure breeding topaz strain is crossed to the pure breeding yellow strain. The phenotype of the F1 flies will be

A. wild type B. yellow eyes C. topaz eyes D. an intermediate phenotype

44 The F1 flies are interbred to produce the F2 generation. The phenotypic ratio of the F2 generation flies is expected to be

A. 7 wild-type : 9 yellow eye B. 3 yellow eye : 1 wild-type C. 9 wild-type : 7 yellow eye D. 1 wild type: 1 yellow eye:

45 The F1 flies are crossed to a pure breeding strain with yellow eyes. In the offspring of this cross the phenotypic ratio is 3 yellow eyes: 1 wild-type. The genotype of this pure breeding strain with yellow eyes is

A. yy ; t t B. yy ; t + t + C. y+y; t t + D. y+y; t + t +

43A, 44C, 45A

I have no idea how to answer question 43-45. Kindply please explain to me. Thank you in advance ! :)

Answer 1