Question

Wild type flies have smooth eyes. Seven different true-breeding strains of fly with rough eye phenotype have been identified (A-G). In each strain, the rough eye trait is due to an autosomal recessive allele. To determine how many genes are involved in eye morphology in these flies, complementation analysis is performed between strains. The offspring phenotypes resulting from each cross are observed. (+: wild-type; -: mutant). Based on these data how many genes are mutant in all of these strains collectively?

A B C D E F    G

A _ _ + + _ + +

B _ + + _ +   +

C _ _ +   + +

D _   +    + +

E _ + +

F _ _

G _

A. 7

B. 2

C. 4

D. 3

Answer 1

Answer is D) 3.

The question is solved ny 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.

Now look in the table, + indicates wild type. - indicates mutants type.

​​​​​​gene 1 has A, B and E mutation.

gene 2 has C and D mutation

gene 3 has F and G mutation.

that's why there are 3 genes.

please rate high..