Question

You are examining the Psf gene and it is known that Psf is normally produced when cells are exposed to high levels of both Ca^2+ and Mg^2+. MetA, MetB, and MetC are important for binding to the promoter of the Psf gene and are involved in regulating its transcription. MetA binds to the A site in the promoter region, MetB binds to the B site, and MetC to the C site. You create binding site mutations in the A,B, and C sites and observe what happens to transcription of the Psf gene. Your results are summarized in a table pictured.

Which of the following proteins are likely to act as GENE REPRESSORS?
(a) MetA only
(b) MetB only
(c) MetC only
(d) MetA and MetC

Answer 1

The proteins that are likely to act as gene repressors in the context of the Psf gene are D. MetA and MetC.

Step-by-step explanation:

This conclusion can be drawn from the information provided about the binding site mutations in the A, B, and C sites and their effects on transcription of the Psf gene.

Firstly, it is known that Psf gene is normally produced when cells are exposed to high levels of both Ca^2+ and Mg^2+. In the absence of these ions, Psf gene transcription might be inhibited. This suggests a regulatory mechanism involving gene repression.

Secondly, the information states that MetA, MetB, and MetC bind to specific sites in the promoter region of the Psf gene and regulate its transcription. If mutations in the A, B, and C sites of the promoter lead to a decrease in Psf gene transcription, it suggests that MetA, MetB, and MetC are involved in gene activation.

Therefore, mutations in these binding sites could result in partial or complete gene repression, indicating that these proteins act as gene repressors when they are unable to bind to the promoter region. The correct answer is D. MetA and MetC.