NEET BIOLOGY

Detailed explanation-1: -The I gene codes for the repressor of the lac operon. The Z gene codes for -galactosidase, which is primarily responsible for the hydrolysis of the disaccharide lactose into its monomeric units, galactose and glucose. The Y gene codes for permease, which increases permeability of the cell to -galactosides .

Detailed explanation-2: -Final answer: In the lac operon system, the lac i gene codes for repressor.

Detailed explanation-3: -The lacI gene codes for a protein called “the repressor” or “the lac repressor", which functions to repressor of the lac operon. The gene lacI is situated immediately upstream of lacZYA but is transcribed from a lacI promoter. The lacI gene synthesizes LacI repressor protein.

Detailed explanation-4: -The lac repressor is a protein that represses (inhibits) transcription of the lac operon. It does this by binding to the operator, which partially overlaps with the promoter. When bound, the lac repressor gets in RNA polymerase’s way and keeps it from transcribing the operon.

Detailed explanation-5: -The lac genes encoding enzymes are lacZ, lacY, and lacA. The fourth lac gene is lacI, encoding the lactose repressor-"I” stands for inducibility. One may distinguish between structural genes encoding enzymes, and regulatory genes encoding proteins that affect gene expression.