Question

A male with singed bristles appeared in a culture of Drosophila. To determine if this phenotype was due to an X-linked mutation

a. Perform a dihybrid intercross, and expect an F2 ratio of 9:3:3:1 in males and females

b. Perform a monohybrid intercross, and expect an F2 ratio of 1:1 in males and females

c. Perform a monohybrid intercross, and expect an F2 ratio of 3:1 in males and females

d. Perform a dihybrid testcross, and expect an F2 ratio of 1:1:1:1 in males and females

e. None of the above

Answer 1

The male with singed bristles appeared in a culture of Drosophila.It is likely that he is the result of a new mutation. There wouldbe no pedigree of his parents and grandparents to examine.

The best way to determine if this phenotype was due to a X-linkedmutation would be through the use of reciprocal crosses asfollows:

P singed male wild type (homozygous) female

the reciprocal cross:
wildtype male X singed (homozygous) female

If the F1 and F2 progeny of these crosses do not show the samepattern of inheritance for the singed phenotype, then it makes adifference whether the allele is being passed to offspring from themale parent or the female parent. You can conclude that themutation is X-linked.