Question

Transcription of the developmental gene M is influenced by two different proteins: B and H. Studies of single and double mutants generated the following information:
In mutants lacking B, transcription of M does occur
In mutants lacking H, transcription of M does not occur.
In double mutants lacking B and H, transcription of M does occur.
Based on this information, put these genes in order in a developmental pathway. Use arrows and t-bars between the genes as appropriate. Choose the correct identity of each below.
Gene 1 1st Symbol Gene 2 2nd Symbol Outcome

Answer 1

Answer:

B --I H >> M transcribed

Explanation:  

Reverse genetics is a classical approach used in molecular genetics to elucidate gene function in a signaling gene network. This technique consists of producing loss of function mutations in genes of interest in order to analyze their phenotypic effects in the downstream signaling pathway.  

In this case, the mutation in B didn't affect the expression of the developmental gene M, together with the other mutant lines, this experiment indicates that B is a downstream suppressor of H (since further experiments show that B plays a role in the signaling pathway). Moreover, the mutation in the gene H affects the expression of M, thereby showing that H acts as a downstream activator of M. Finally, B-H double mutants did neither affect the expression of M, thereby showing that M transcription is dependent of the interaction between B and H.