The wild?type fruit fly, Drosophila melanogaster, has large compound eyes and no

Question

The wild?type fruit fly, Drosophila melanogaster, has large compound eyes and normal (un?notched) wings. Mutant strains have been isolated that have either eyes that are reduced in size or notched wings. The genes representing these two mutant traits are located on separate autosomes. The following data were generated by five different crosses.

a. For each mutation, determine whether it is dominant or recessive and justify your answer.

b. Define gene symbols and, for each cross, determine the genotypes of the parents. (Assume homozygosity unless there is evidence to the contrary.)

The wild type fruit fly, Drosophila melanogaster, has large compound eyes and normal (un notched) wings. Mutant strains have been isolated that have either eyes that are reduced in size or notched wings. The genes representing these two mutant traits are located on separate autosomes. The following data were generated by five different crosses. a. For each mutation, determine whether it is dominant or recessive and justify your answer. b. Define gene symbols and, for each cross, determine the genotypes of the parents. (Assume homozygosity unless there is evidence to the contrary.)

Explanation / Answer

Notched wings is recessive. In cross 2 when a cross occurs between normal, large X normal, large = normal : notched wings occurs in 3:1 (given, 122 normal wings, and 41 notched wings.).

Reduced eyes are dominant. In cross 4, cross is shown between notched, reduced X notched, reduced = reduced : large eyes are found in 3:1 ratio (given 132 reduced eyes, and 44 large eyes.)

Genotypes of parents :- Let us assume R for reduced eye, r for large eye, N for normal wings and n for notched wings.

Cross 1. NnRr X NnRr

Cross 2. Nnrr X Nnrr

Cross 3.NnRr X nnrr (It is a test cross)

Cross 4: nnRr X nnRr

Cross 5: nnRr X NnRr

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