Quizzes 5 and 6 Multiple Choice

A mutagen that alkylates bases is: A. ethyl methanesulfonate (EMS) B. UV light C. proflavin D. 2-aminopurine

A

If a human cell has two Barr bodies then the genotype of the individual could be: A. XXXY B. XXXXY C. XXY D. XYY

A

In the Ames test, a ( ) number of colonies is observed if a substrate ( ) a mutagen, compared with the control that is not exposed to the suspected mutagen. A. significantly higher, is B. significantly higher, is not C. significantly lower, is D. similar, is

A

Which of the following conditions would cause transcription to be activated? A. a repressor plus an inducer B. a repressor plus a corepressor C. an activator plus an inhibitor D. none of the above

A

An advantage of translesion DNA polymerases is they can replicate ( ), but a disadvantage is they ( ). A. very quickly, have low fidelity B. over damaged DNA, have low fidelity C. over damaged DNA, are very slow D. very accurately, are very slow

B

An up promoter mutation causes the promoter of a gene to be......................like the consensus sequence and .........................transcription A. less, stimulates B. more, stimulates C. less, inhibits D. more, inhibits

B

For X chromosome inactivation to occur, where are the Xist an Tsix genes expressed? (Xa: active X chromosome, Xi: inactive X chromosome) A. Xist is expressed only on Xa, and Tsix is expressed only on Xi B. Xist is expressed only on Xi, and Tsix is expressed only on Xa C. both Xist and Tsix are expressed on Xa D. both Xist and Tsix are expressed on Xi

B

In one cell, gene A is expressed, whereas in another cell, gene A is inactive. After these cells are fused experimentally, both copies of gene A are expressed. This observation could be explained by: A. a cis-epigenetic mechanism B. a trans-epigenetic mechanism C. DNA methylation D. both a and b

B

In the replica-plating experiments of the Lederbergs, bacterial colonies appeared at the same locations in each of two secondary plates, because: A. T1 phage caused the mutations to happen B. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating C. both a and b D. the mutations occurred on the secondary plates after T1 exposure and replica plating

B

Methylation of CpG islands: A. changes the chromatin to an open conformation B. prevents binding of activator protein to enhancer C. prevents the initiation of DNA replication D. interferes directly with RNA polymerase binding

B

The bind of ______ to the lac repressor disables the lac repressor to bind to the ____ site, thereby _____ transcription. A. glucose, CAP, and inhibiting B. allolactose, operator, and increasing C. glucose, CAP, and increasing D. allolactose, operator, and inhibiting

B

The expression of a single allele is associated with which of the following? A. X-inactivation B. genomic imprinting C. maternal inheritance D. extra nuclear inheritance

B

What is an operon? A. a site in the DNA where transcription begins B. a group of genes under the control a single promoter C. a sequence in an mRNA which mediates stem-loop formation D. all of the above

B

When tryptophan levels are low, the ____ stem-loop forms and transcription ____ the trpL A. 2-3, ends just past B. 2-3, continues beyond C. 3-4 ends just past D. 3-4, continues beyond

B

Which of the following characteristics is typical of a eukaryotic gene that can be transcribed? A. the core promoter is wrapped around a nucleosome B. the core-promoter is found in a nucleosome-free region C. the terminator is wrapped around a nucleosome D. none of the above are correct

B

Which of the following is an example of germline mutation? A. a mutation in an embryonic muscle cell B. a mutation in a sperm cell C. a mutation in an adult nerve cell D. a mutation in an adult skin cell

B

Which of the following mediates the interaction between regulatory transcription factors and RNA polymerase? A. TFIIF and mediator B. TFIID and mediator C. TFIID and TFIIB D. TFIIB and mediator

B

A bidirectional enhancer has the following sequence: 5'-GTCA-3' / 3'-CAGT-5' Which of the following sequences would also be a functional enhancer? A. 5'-ACTG-3' / 3'-TGAC-5' B. 3'-GTCA-5' / 5'-CATG-3' C. 5'-TGAC-3' / 3'-ACTG-5' D. 3'-TGAC-5' / 5'-ACTG-3'

C

Patients with Xeroderma pigmentosum are highly susceptible to ( ), as they have a defect in ( ). A. colon cancer, mismatch repair B. breast cancer, repair of DNA double strand breaks by homologous recombination C. skin cancer, nucleotide excision repair D. skin cancer, photolyase

C

What is the mechanism by which X-rays induce mutations? A. creating thymine dimers B. alkylating bases C. inducing DNA double-stranded breaks D. intercalation

C

A mutation that does not change the amino acid sequence of a polypeptide is: A. missense mutation B. nonsense mutation C. neutral mutation D. silent mutation

D

Regulatory transcription factors can be modulated by: A. the binding of small effector molecules B. protein-protein interactions C. covalent modifications D. all of the above

D

Translation can be related by: A. translational repressors B. attenuation C. antisense RNA D. both a and c

D

What is the molecular mechanism for imprinting a gene? A. acetylation B. nitration C. phosphorylation D. methylation

D

Which of the following is not an example of a spontaneous mutation? A. a mutation caused by depurination B. a mutation caused by tautomeric shift C. a mutation caused by deamination D. a mutation caused by X-rays

D