Question

GENITICS UNIT VIA NAME 30) Present a detailed description of the actions of the regulatory protein systems. "y proteins in inducible and repressible name Give the names of the components of an Operon In the lac operon, the product of structural gene lacZ is capable of A) nonautonomous replication B) forming lactose from two glucose molecules C) replacing hexokinase in the early steps of glycolysis D) splitting the e-linkage of lactose E) forming ATP from pyruvate Compare and contrast positive and negative control of gene expression in bacteria. OBJ 31) Define Allosteric Control: OBJ31) Certain mutations in the regulator gene of the lac system in E.coli result in maximal synthesis of the lac protei (5-galactosidase, etc.) even in the absence of the inducer (lactose). Provide an explanation for this observation

Answer 1

30 - Different components of an operon are

(1) Promoter - nucleotides sequence which initiate the transcription.

(2) Operator - nucleotides sequence to which repressor binds.

(3) Structural - Nucleotides sequence which are regulated by operon for protein synthesis.

(4) Regulator - Nucleotides sequence which produces repressor.

The product of lac z gene is Beta galactosidase which (D) split the lactose into glucose and fructose.

Negative control of gene expression is done by the binding of repressor to promoter and thus inhibits the operon and RNA polymerase is not recruited in this control .

Positive control is binding of inducer to the promoter thus induces the protein synthesis with the help of RNA polymerase.

31) Allosteric control is binding of effector with enzyme on the site other than its active site. The inhibition of reaction by the feedback molecules is also an example.

Mutation of Regulator gene leads to the production of inactive repressor which fails to inhibit the operon thus lac genes ( Z) gets over active for the production of protein even in absence of lactose or inducer.