Consider three genes Gene A Gene B and Gene C Mutants of all

Consider three genes, Gene A, Gene B, and Gene C. Mutants of all three cause defects during early Drosophila development. We want to know how they interact with each other, so we generate null mutations in each of these genes.

In a Gene B mutant, Gene C is not expressed. What is the likely relationship between Gene B and Gene C?

In a Gene C mutant, Gene A mRNA is expressed in a larger part of the embryo than in a wild type embryo. What is the likely relationship between Gene A and Gene C?

In a Gene A mutant, the expression of Gene C and Gene B are unchanged. What does this tell us about the relationship among the genes?

In a Gene B mutant, Gene A mRNA is expressed in a larger part of the embryo than in the wild type embryo. Draw a genetic pathway that explains the relationship among all three of these genes.

Solution

the product of gene B binds to gene C and helps in transcription of gene C. because of mutation in gene B, product of gene B will not form and it will not activate gene C transcription.

the product of gene C binds to gene A and inhibit transcription of gene A. because of mutation in gene C, product of gene C will not form and it will not inhibit gene A transcription.

mutation in gene A has no effect on gene B and gene C transcription.

the product of gene B binds to gene A and inhibit transcription of gene A. because of mutation in gene B, product of gene B will not form and it will not inhibit gene A transcription.