An operon of genes encoding enzymes in a biosynthetic pathway is likely to be which of the following?

inducible

repressible

constitutive

monocistronic

repressible

Explanation:

When the expression of genes of an operon is reduced or decreased in response to certain signals, the operon is said to be repressible operon. The operon with genes that code for enzymes of biosynthetic pathways is repressible in nature to ensure the expression of the genes only when required.

For example, the genes of tryptophan operon code for the enzymes involved in the biosynthesis of tryptophan. The "tryptophan operon" is not expressed when enough tryptophan supplies are available for the cell. So, tryptophan operon is a repressible operon.