The trp operon consists of how many genes encoding tryptophan biosynthesis enzymes?

The trp operon consists of how many genes encoding tryptophan biosynthesis enzymes?

• A. 5
• B. 3
• C. 4
• D. 6

Answer: (A)

In bacteria, genes for a single biosynthetic pathway are clustered in an operon so their expression is coordinated. For tryptophan synthesis, the trp operon contains five structural genes that code for the enzymes driving the pathway from chorismate to tryptophan. The gene products are TrpE, TrpD, TrpC, TrpB, and TrpA. Notably, TrpC is a bifunctional enzyme, performing two catalytic activities within one polypeptide, which means there are six enzymatic steps in the pathway but only five genes encoding them. So the trp operon consists of five genes encoding tryptophan biosynthesis enzymes.

In bacteria, genes for a single biosynthetic pathway are clustered in an operon so their expression is coordinated. For tryptophan synthesis, the trp operon contains five structural genes that code for the enzymes driving the pathway from chorismate to tryptophan. The gene products are TrpE, TrpD, TrpC, TrpB, and TrpA. Notably, TrpC is a bifunctional enzyme, performing two catalytic activities within one polypeptide, which means there are six enzymatic steps in the pathway but only five genes encoding them. So the trp operon consists of five genes encoding tryptophan biosynthesis enzymes.