Question

Part a the presence of a mutant lac repressor that could not bind lactose would result in _______ transcription even when lactose was present because the mutant repressor would remain bound to the lac __________ see section 18.3 (page 373) . view available hint(s) the presence of a mutant lac repressor that could not bind lactose would result in _______ transcription even when lactose was present because the mutant repressor would remain bound to the lac __________ see section 18.3 (page 373) . no; operator lots of; operator lots of; promoter no; promoter

Answer 1

The presence of a mutant lac repressor that could not bind lactose would result in no transcription even when lactose was present because the mutant repressor would remain bound to the lac operator 

The transcription of lac operator is controlled by the lac repressor. When lactose is present, the lac repressor normally will bind to the lactose, removing itself from the lac operator so it could be transcripted. 
In this case, the mutation makes the lac repressor keep binding to the lac operator so the result would be no transcription even when lactose present.

Answer 2

The presence of a mutant lac repressor that could not bind lactose would result in no transcription even when lactose was present because the mutant repressor would remain bound to the lac operator.

Further Explanation:

When lactose is unavailable, the repressor molecule binds to the DNA and prevents transcription of the genes. Therefore, the enzyme that is required for the lactose metabolism will not be produced. Comparatively, in the presence of lactose, the repressor molecule will bind to inducer (allolactose), which prevents binding of the repressor to DNA results in transcription of a gene. Enzymes accountable for the lactose metabolism will be produced. The mutated repressor molecule, which prevents binding to DNA, will result in the production of enzymes all the time, irrespective of the presence or absence of lactose. Genes responsible for the metabolism of lactose will be expressed all the time. If a mutation occurs in the repressor, it will prevent inducer binding. The repressor molecule will bind then to DNA permanently and blocks the activity of RNA polymerase. This results in no transcription and translation of operon. Presence of a mutated operator that does not allow the binding of a repressor would cause constitutive expression of the operon.

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Answer Details:

Grade: High School

Subjects: Biology

Chapter: Genetics

Keywords:

Lactose, metabolism, genes, produce, DNA, allolactose, repressor, transcription, repressor, operon, binding, enzyme, absence.