Chapter 26 Self-test questions

. In the context of prokaryotic gene expression, which of the following is the most appropriate definition of an operator?

A cluster of genes that are regulated by a single promoter.

A DNA-binding protein that regulates gene expression.

A non-coding, regulatory DNA sequence that is bound by RNA polymerase.

A non-coding, regulatory DNA sequence that is bound by a repressor protein.

. In terms of lac operon regulation, what happens when E. coli is grown in medium containing both glucose and lactose?

Both CAP and the lac repressor are bound to the DNA.

CAP is bound to the DNA but the lac repressor is not.

Lac repressor is bound to the DNA but CAP is not.

Neither CAP nor the lac repressor are bound to the DNA.

. Which of the following can be described as 'a sequence that can be several thousand base pairs upstream or downstream of a eukaryotic promoter and which increases gene expression as much as 200-fold.'?

CAAT box.

Enhancer.

Insulator.

TATA box.

. Nuclear receptors belong to which class of transcription factor?

Helix-loop-helix proteins.

Helix-turn-helix proteins.

Leucine zipper proteins.

Zinc finger proteins.

. What best describes the mechanism by which the coactivator CREB-binding protein (CBP) activates transcription?

CBP has DNA methyltransferase activity.

CBP has histone acetyl transferase activity.

CBP interacts with the basal transcription complex.

CBP interacts with the basal transcription complex and also has histone acetyl transferase activity.

. Which of the following statements, concerning regulation of trp operon expression by attenuation, is correct?

The leader peptide sequence encodes enzymes required for tryptophan synthesis.

The leader peptide sequence contains no tryptophan residues.

Rapid translation of the leader peptide allows completion of the mRNA transcript.

Rapid translation of the leader peptide prevents completion of the mRNA transcript.

. Which of the following statements regarding regulation of transferrin-receptor protein synthesis is correct?

The iron-responsive element is an iron-binding sequence in the mRNA that encodes transferrin-receptor protein.

The iron-responsive element is in the 5' untranslated region of the mRNA that encodes transferrin-receptor protein.

When iron is abundant the IRE-binding protein binds to and stabilizes the mRNA that encodes transferrin-receptor protein.

When iron is scarce the IRE-binding protein binds to and stabilizes the mRNA that encodes transferrin-receptor protein.

. 'RNAi' stands for which of the following?

RNA inducer.

RNA insertion.

RNA interference.

RNA intron.

. Suppose a certain gene contains the double-stranded sequence:
5'- ATGTTTAGCGCC -3'
3'- TACAAATCGCGG -5'
If the top strand is the sense strand and codes for an mRNA whose sequence begins 'ATG', which of the following would be the sequence of the corresponding segment of antisense RNA?

5'-AUGUUUAGCGCC-3'

5'-CCGCGAUUUGUA-3'

5'-GGCGCUAAACAU-3'

5'-UACAAAUCGCGG-3'

. The effectors of gene silencing are short double-stranded RNA molecules produced by the action of the enzyme dicer. Approximately what size are these molecules?

11 bp.

22 bp.

75 bp.

100 bp.

. Which of the following is true of the lac operon in E. coli?

The operon is only switched on in the absence of lactose in the growth medium.

The lac operon messenger RNA is a polycistronic mRNA (it carries information for synthesis of several proteins).

The enzyme β-galactosidase is only produced in large quantities when the lac repressor is bound to the operator.

The promoter is the binding site for the lac repressor.

. Which of the following statements about mRNA stability is correct? Please select all that apply.

Prokaryotic mRNAs have a half-life of only a few minutes.

Regulation of mRNA stability is a way of regulating gene expression.

It is thought that polyA tails stabilise eukaryotic mRNAs.

Histone mRNAs have especially long polyA tails and are especially stable.

. An epigenetic change in gene expression is an inherited change that does not involve any change in the nucleotide sequence of the gene. True or false?

True.

False.

. Which of the following statements is true of RNA interference?

RNA interference is a normal way for organisms to regulate gene expression.

RNA interference is a mechanism for combating virus infection in plants.

RNA interference occurs only in vertebrates.

RNA interference is already used therapeutically for many disorders.

Chapter 26 Self-test questions

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