A) three
B) four
C) two
D) five
Correct Answer: A
Solution :
Lac operon is inducible operon that regulates genetic material, which remains switched off normally but becomes operational in the presence of an inducer. Its components are (i) Structural gene Which produces mRNAs forming forming polypeptides/ protein. Z \[\to \] Produces enzyme \[\beta \]-galactosidase Y \[\to \] Produces enzyme galactoside permease A \[\to \] Produces enzyme transacetylase. (ii) Operator gene gives passage to RNA polymer, when structural genes are to express themselves. (iii) Promoter gene It is recognition centre for RNA polymerase of the operon. The promoter region contains three segments. (iv) Regulator gene It produces a represser that binds to operator gene for keeping it nonfunctional. (v) Represser It is a small protein formed by regulator gene, which binds to operator gene and blocks passage of RNA-polymerase towards structural genes. (vi) Inducer It is a chemical, which attaches to represser, changes the shape of operator binding site so that represser no more remains attached to operator.
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