QUESTION 3 Which of the following is correct regarding the Lac operon? If lactos

Question

QUESTION 3

Which of the following is correct regarding the Lac operon?

If lactose is absent, the repressor does not bind to the operator.

If ;lactose is absent, the RNA polymerase binds to the operator.

If ;lactose is present, the repressor binds to the operator.

If ;lactose is present, the RNA polymerase binds to the promoter region.

1 points   

QUESTION 4

For the lac operon genes to be expressed, ___________.

Lactose has to be present.

Lactose has to be absent.

It has nothing to do with lactose.

None of the above.

1 points   

QUESTION 5

A bacterial strain has a new mutation. As the result of the mutation, the bacteria no longer respond to lactose. Specifically, the three structural genes are expressed regardless of the presence of lactose. Speculate where the mutation might be.

The promoter region

The operator region

The Lac Z gene

The Lac Y gene

1 points   

QUESTION 7

Which of the following is not a difference between transcription in eukaryotes and prokaryotes?

Eukaryotes use enhancers but prokaryotes do not.

The promoter sequences are different.

RNA polymerases are different.

Eukaryotes have splicing, but prokaryotes do not.

1 points   

QUESTION 8

For a codon GGU, how many anticodons can base pair with it?

1

2

3

4

1 points   

QUESTION 9

If a tRNA has the anticodon sequence of 3' CCA 5', which AA should be attached to it?

Pro

Gly

Ala

Asn

1 points   

QUESTION 10

which part of the ribosome carries the peptidyl transferase activity?

16S rRNA

Small subunit proteins

large unit proteins

23S rRNA

If lactose is absent, the repressor does not bind to the operator.

If ;lactose is absent, the RNA polymerase binds to the operator.

If ;lactose is present, the repressor binds to the operator.

If ;lactose is present, the RNA polymerase binds to the promoter region.

Explanation / Answer

Allolactose (modified form of lactose) is required for removing the lac repressor that is bound to the operator region of the lac operon. Only if the repressor is removed, the RNA polymerase can transcribe the lac genes by binding to the promoter region.

QUESTION 3

Which of the following is correct regarding the Lac operon?

D. If ;lactose is present, the RNA polymerase binds to the promoter region.

QUESTION 4

For the lac operon genes to be expressed, ___________.

A. Lactose has to be present.

QUESTION 5

A bacterial strain has a new mutation. As the result of the mutation, the bacteria no longer respond to lactose. Specifically, the three structural genes are expressed regardless of the presence of lactose. Speculate where the mutation might be.

B. The operator region

In the operator region, the lac repressor binds and prevents the RNA polymerase from transcribing the lac genes. Mutation in the operator region will facilitate the transcription by RNA polymerase with or without the presence of Lactose.

QUESTION 7

Which of the following is not a difference between transcription in eukaryotes and prokaryotes?

A. Eukaryotes use enhancers but prokaryotes do not.

Like eukaryotes, a number of enhancer-binding proteins activate transcription by specialized forms of RNA polymerase in prokaryotes.

QUESTION 8

For a codon GGU, how many anticodons can base pair with it?

D. 4

CCA, CCG, CCU, CCC (Based on Wobble hypothesis which states that one tRNA molecule (with one amino acid attached) can recognise and bind to more than one codon, due to the less-precise base pairs that can arise between the 3rd base of the codon and the base at the 1st position on the anticodon.

QUESTION 9

If a tRNA has the anticodon sequence of 3' CCA 5', which AA should be attached to it?

B. Gly

QUESTION 10

which part of the ribosome carries the peptidyl transferase activity?

D. 23S rRNA

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