Question

! Required information Fruit flies normally have red eyes. Seven different true-breeding strains of fly with white eyes have been identified (A-G). In each strain, the white eye trait is due to an autosomal recessive allele. It is possible all seven strains have mutations in the same gene. Alternatively, they may have mutations in different genes. To determine how many genes are involved in eye color in these flies, pair-wise crosses are performed between each strain. The offspring phenotypes resulting from each cross are observed. (+ = wild-type; = mutant) A B с E F G A D + + Flies from strains Cand D mate and produce offspring. Do the offspring have red eyes?

Answer Choices:

A) No

B) More information is needed to determine eye color

C) Yes

Answer 1

The questiom is solved on the basis of complementation test.

Complementation is used to detect whether two mutants are in the same gene or found in the different genes.

In this test, we cross two parents Which are homozygous recessive for two different mutations. If there is found wild type progenies. This suggests that there is found complementation between two mutations and two mutations are found in different genes.

Similarly if the progenies are of mutant type, then complementation does not occurs between two mutations and the mutations are found in same gene.

Here + indicates red eye color. - indicates white eye color.

That's why:

A, B and E mutations are in gene 1.

C and D mutations are in gene 2.

F and G mutations are in gene 3.

The crossing between C and D produce white eye color progenies. Because complementation does not occur between C and D mutations because they are found in same genes.

Answer is : A (no).

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