Answer to Question #339028 in Genetics for neezy

Question

Deduce and explain the effects of mutations:

a) in the operator, so that the repressor is no longer able to bind.

b) in lacI, so that the repressor is no longer synthesized.

c) in the promoter, so that RNA polymerase no longer binds.

d) in lacI, so that the repressor no longer binds to lactose.

e) in lacY that causes transcription to terminate in the middle of the gene.

f) location unknown, which prevents the lac mRNA from being degraded. 

Answer 1

(a) if a repressor is not attached to the operator, then transcription of the operon genes occurs regardless of the presence or absence of a substrate;

(b) the same situation as in paragraph (a), that is, in the absence of a repressor, transcription of the operon genes is carried out regardless of whether there is a substrate or not;

(c) if RNA polymerase does not attach to the promoter, then transcription of operon genes is not carried out regardless of whether there is an inhibitor or not;

(d) in the absence of lactose attachment to the repressor, the latter does not detach from the operator, and transcription of operon genes does not occur, regardless of whether there is lactose or not;

(e) if only the first half of the LacY gene is transcribed, then as a result, a functional analogue of the product of this gene is not expressed, which is normally an enzyme that utilizes lactose, as a result of which the bacterium does not survive in a medium with the addition of lactose, since it is not able to ferment it;

(f) if the lac mRNA is degraded, then no expression products of the lactose operon genes are formed, which means that the bacteria cannot ferment lactose.