Question

Which of the following is an example of positive gene regulation?

• A. The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.
• B. The lac gene, in which the repressor preventing the synthesis of the enzymes that degrade lactose is deactivated by the presence of lactose.
• C. CAP, which acts as a required transcription factor for the enzymes that degrade lactose.
• D. All of the above.

Answer 1

Answer: (A)

The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.

Regulation of functioning of the expression of genes is known as the regulation of gene expression. It is basically of three types- inducible, constitutive and repressible.

The repressible kind of control is when the product of regulatory gene initiates the expression of the gene under its control.

The tryptophan consists of repressible Operon model in which when the end product tryptophan is present in sufficient amount it's molecules act as corepressor and the structural genes become switched this is also known as feedback repression or positive regulation.

So, the correct option is 'The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.'