Question

Please answer the following question related to genetics-regulation of gene expression in eukaryote

You are checking how different molecules affect gene expression. Based on the data below, write what kind of genes might be affected by the molecules and what could be the role of each molecule… (30)

Molecule	Effect when present	Effect when absent
A	4 proteins are produced in normal quantity	No proteins are produced no matter which other molecules we add
B	No proteins are produced (or in extremely small quantity)	4 proteins are produced in normal quantity – if A is present
C	4 proteins are produced in large quantities if D and E are present	4 proteins are produced in normal quantity – if A is present
D	4 proteins are produced in large quantities if C and E are present	4 proteins are produced in normal quantity – if A is present
E	4 proteins are produced in large quantities if C and D are present	4 proteins are produced in normal quantity – if A is present
F	No proteins are produced (or in extremely small quantity) if C is present	4 proteins are produced in normal quantity – if A is present

Answer 1

Molecule A is RNA polymerase, which binds to promoter of the 4 genes (presumably a 4gene operon) and caused basal level transcription. Without RNA pol, no transcription is possible with any other protein.

Molecule B is a repressor of this operon, that binds some operator region or regulatory region of this operon and represses transcription. Absence causes basal level transcription in presence of RNA pol.

Molecules C, D, E are all co-activators that bind together to an enhancer sequence near this operon and causes high level transcription. All three are needed for this function and neither works except the other two. Their absence causes basal level transcription by RNA pol.

Molecule F acts as a repressor in presence of molecule C. They bind to the operator region together and repress transcription.