Single Choice

The lac operon consists of

AThree regulatory genes and three structural genes.
BFour regulatory genes only.
COne regulatory gene and three structural genes.
Correct Answer
DTwo regulatory genes and two structural genes.

Solution

Lac operon is made up of one regulator, one operator and three structural genes. The three structural genes are LacZ, LacY and LacA. LacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. LacY encodes beta permease which pumps the lactose inside the cell. Lac A encodes beta transacetylase which removes toxic substances from the cell.
The regulator gene produces m-RNA which translates into the repressor. The repressor attaches to the operator and blocks the expression of the structural gene in absence of inducer. In presence of inducer, the repressor attaches to the inducer and operator is not blocked so it allows the expression of the structural gene. Operator genes are a region of DNA sequence which attaches to the repressor molecule and stops the expression of the structural gene.
So, the correct answer is option C.

SIMILAR QUESTIONS

Genetics

Which of the following is required as inducer(s) for the expression of Lac operon?

Genetics

All of the following are part of an operon except

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Gene regulation governing lactose operon of E.coli that involves the lac I gene product is

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In the lac operon model, lactose molecules function as

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In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down sometime after addition of lactose in the medium?

Genetics

Choose the correct answer from the alternatives given : The sequence of structural genes in lac operon is

Genetics

Choose the correct answer from the alternatives given : In E. Coli, the lac operon gets switched on when

Genetics

Choose the correct answer from the alternatives given : In E. Coli, the lac operon gets switched on when

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