Question

Which parts of the DNA region shown in the diagram encode proteins? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator).

a) I
b) Z, Y, A
c) P
d) O

Answer 1

The parts that encode proteins in the lac operon are the Z, Y, A structural genes, responsible for enzymes in lactose metabolism, while the I gene produces the regulatory lac repressor protein; P and O are regulatory regions. Option number b is correct.

Step-by-step explanation:

The parts of the DNA region that encode proteins in the diagram provided are the Z, Y, A which are the lac operon structural genes. These genes encode for proteins involved in lactose metabolism: lacZ encodes for β-galactosidase, lacY for lactose permease, and lacA for transacetylase.

The I gene encodes the lac repressor, which is a regulatory protein and not an enzyme or a structural component of the cell. The P (promoter) and the O (operator) are not genes but regulatory elements that control the expression of the Z, Y, A genes by allowing or blocking the binding of RNA polymerase and, consequently, transcription.