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Q.
The promoter region in a lac operon is distinguishable into the following number of segments
AMUAMU 2004
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 mRNA's forming forming polypeptides/ protein.
$Z \rightarrow$ Produces enzyme $\beta$-galactosidase
$Y \rightarrow$ Produces enzyme galactoside permease
$A \rightarrow$ Produces enzyme transacetylase.
(ii) Operator gene gives passage to RNA polymer, when structural genes are to express themselves.
(iii) Promoter gene It is recognition center for RNA polymerase of the operon. The promoter region contains three segments.
(iv) Regulator gene It produces a repressor that binds to operator gene for keeping it nonfunctional.
(v) Repressor It is a small protein formed by regulator gene, which binds to operater gene and blocks passage of RNA-polymerase towards structural genes.
(vi) Inducer It is a chemical, which attaches to repressor, changes the shape of operator binding site so that repressor no more remains attached to operator.