Answer to Question #104878 in Molecular Biology for Kylie

Question

Which of the following is true of the lac operon in E. coli?
1. The operon is only switched on in the absence of lactose in the growth medium.
2. The lac operon messenger RNA is a polycistronic mRNA (it carries information for
synthesis of several proteins)
3. The enzyme β-galactosidase is only produced in large quantities when the lac
repressor is bound to the operator.
4. The promoter is the binding site for the lac repressor.

Answer 1

2. The lac operon messenger RNA is a polycistronic mRNA (it carries information for

synthesis of several proteins).

The lac operon mRNA consists of several coding sequences that produce enzymes required for lactose metabolism. The production of the mRNA is controlled by a single promoter. As a result, this mRNA is polycistronic.