Question

Which is a DNA-binding protein?

(a) repressor

(b) operator

(c) luciferase

(d) thymidine

I have been asked this question by my college professor while I was bunking the class.

Origin of the question is Gene Expression Control in portion Control of Gene Expression of Cell Biology

Answer 1

The correct answer is:

(a) repressor

Explanation:

A repressor is a DNA-binding protein that can bind to specific sequences in the DNA, such as the operator region of an operon. When bound, the repressor can inhibit the transcription of adjacent genes, thus regulating gene expression. This is a key component in operon systems like the lac operon in bacteria, where the repressor binds to the operator to prevent RNA polymerase from transcribing the genes involved in lactose metabolism when lactose is not present.

The other options are not DNA-binding proteins:

• Operator is a DNA sequence, not a protein.
• Luciferase is an enzyme involved in light production and is not a DNA-binding protein.
• Thymidine is a nucleoside involved in DNA synthesis, not a protein.