Question

A transcriptional repressor that controls the transcription of gene A is not normally active unless bound by an effector molecule X. In a certain cell, the domain of the repressor that binds to the silencer of gene A is mutated so that the repressor-X complex can no longer bind to its recognition site. With all other factors being the same, what effect do you predict on the transcription of gene A if X is increased in the cell and the cell is already expressing gene A

Answer 1

Answer:

Transcription of gene A is not affected

Explanation:

A transcriptional repressor is a DNA/RNA-binding protein that acts to suppress gene expression and/or protein synthesis by binding to target sequences. Moreover, a silencer is a DNA region that binds to particular transcriptional repressors in order to suppress gene expression. In this case, the transcriptional repressor is activated by binding to an effector molecule X (e.g., another protein). In consequence, and since the activated repressor-X complex is not more able to bind the silencer of gene A, it is expected that such complex will not be able to affect transcription of the target gene.