14. The following table shows the results of a complementation test for eye colo

Question

14. The following table shows the results of a complementation test for eye color mutations in Drosophila. Different mutant strains were crossed to determine if the offspring (Fl generation) could grow (+ or no A) How many genes are involved and which mutations are in the same gene? B) Assuming no recombination takes place, what are the possible phenotypes of the F2 generation that rslt from crossing the offspring of the vermillion and carnation mutant strains? Show the chromosomal configuration of this F2 gencration. cora apricot buff carnation Mutation white white garnet ruby vemillion c arnet rub vermillion che coral buff carnation

Explanation / Answer

The mutants are crossed to yield the offspring which may or may not live, indicated by + or -. The number of mutations and genes are identified by the complementation tests. The mutation withing the same gene cannot complement each other and hence cannot grow. The mutation in different genes can complement each other and grow. The mutant "white" cannot complement with another "white", as they have mutation in same gene. In similar logic, the cherry, apricote, and buff cannot complement with white. so they all habour mutation in same gene. So, these will make one group or gene 1. The garnet can complement with all other mutants, hence it has a mutation in gene 2. Ruby can combine with rest of mutants , so it is mutation in gene 3. vemillion can combine with all, hence gene 4. coral , gene 5; carnation , gene 6. so we have total 6 genes which are mutated.
gene 1: white, cherry, apricote, and buff
gene 2: Garnet
gene 3: Ruby
gene 4: Vermillion
gene 5: coral
gene 6: carnation

The genes for eye color are sex linked and carried by X chromosome. C - normal, V - normal, c-carnation; v - vermillion

vermillion: XCvXCv female (she has normal C genes)
carnation: XVc Y   male ( he has normal V genes)

F1 : XCv XVc ;   XCv Y;
     Normal ; vermillion

F1 female is normal because she has C and V genes which give normal eyes and are dominant to c and v respectively.

F2: XCv XVc ;   XCv Y

XCvXCv   Normal female
XCv Y   Vermillion male
XVcXCv   Normal female
XVc Y   carnation male

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