What does “lac” refer to in what we call the lac operon?

Solution

Lactose operon in E.coli is a catabolic pathway in which the structural genes remain switched off unless the inducer (Lactose) is present in the medium.

DNA finger printing refers to

Solution

DNA finger printing is the technique of determining nucleotide sequences of certain areas of DNA which are unique to each individual. DNA contains non cistronic hypervariable repeat sequences called VNTR. DNA fingerprinting involves the identification of these VNTRs.

In negative operon

Solution

In negative (repressible) operon, the repressor co-repressor complex binds with the operator. The free repressor cannot bind to the operator.

Genes that are involved in turning on or off the transcription of a set of structural genes are called

If the gene encoding the lac repressor is mutated so that it can no longer bind the operator, will transcription of that operon occur?

Yes, but only when lactose is present.
No, because RNA polymerase is need to transcribe the genes.
Yes, because the operator will not be bound by repressor and RNA polymerase can transcribe the lac operon.
No, because cAMP levels are low when the repressor is non-functional.

Solution

If the lac repressor is non functional, it can not bind the operator site and transcription of the lac operon will occur at all times, whether or not lactose is present.

The error rate of changing an incorrect base with another incorrect base during proofreading is

Transcriptional regulation in prokaryotes can occur by

a repressor binding an operator and preventing transcription.
an activator binding up stream from a promoter and positively affecting transcription.
different promoter sequences binding RNA polymerase more tightly, resulting in more effective transcriptional initiation.
All of the above

Solution

Option a refers to the lac and trp repressors, option b to the CRP protein, and option c refers to promoter that have different transcriptional efficiencies.

Which of the following is the first thing that happens when a signal molecule acts on a target cell?

Solution

The first effect of any signal molecule must involve the binding of the molecule to a receptor.

Process used for amplication or multiplication of DNA for finger printing is

Lactose operon produces enzymes

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