AP BIO chapter 15 end of chapter + scenario questions Flashcards

Suppose an experimenter becomes proficient with a technique that allows her to move DNA

sequences within a prokaryotic genome.

If she moves the promoter for the lac operon to the region between the beta galactosidase

(lacZ) gene and the permease (lacY) gene, which of the following would be likely?

1. A) The three structural genes will be expressed normally.
2. B) RNA polymerase will no longer transcribe permease.
3. C) The operon will no longer be inducible.
4. D) Beta galactosidase will not be produced.
5. E) The cell will continue to metabolize but more slowly.

If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene,

which of the following would likely occur when the cell is exposed to lactose?

1. A) The inducer will no longer bind to the repressor.
2. B) The repressor will no longer bind to the operator.
3. C) The operon will never be transcribed.
4. D) The structural genes will be transcribed continuously.
5. E) The repressor protein will no longer be produced

If she moves the repressor gene (lac I), along with its promoter, to a position some several

thousand base pairs away from its normal position, which will you expect to occur?

1. A) The repressor will no longer be made.
2. B) The repressor will no longer bind to the operator.
3. C) The repressor will no longer bind to the inducer.
4. D) The lac operon will be expressed continuously.
5. E) The lac operon will function normally.

A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in

which the transgene has integrated into the yeast genome. In four of the lines, the transgene is

expressed strongly, but in the fifth there is no expression at all.

Which of the following is a likely explanation for the lack of transgene expression in the fifth

cell line?

1. A) The transgene integrated into a heterochromatic region of the genome.
2. B) The transgene integrated into a euchromatic region of the genome.
3. C) The transgene was mutated during the process of integration into the host cell genome.
4. D) The host cell lacks the enzymes necessary to express the transgene.
5. E) The transgene integrated into a region of the genome characterized by high histone

Acetylation.

Of the lines that express the transgene, one is transcribed but not translated. Which of the

following is a likely explanation?

1. A) no promoter
2. B) no AUG in any frame
3. C) no compatible ribosome
4. D) high histone acetylation
5. E) missing transcription factor

A researcher found a method she could use to manipulate and quantify phosphorylation and

methylation in embryonic cells in culture.

In one set of experiments she succeeded in decreasing methylation of histone tails. Which of

the following results would she most likely see?

1. A) increased chromatin condensation
2. B) decreased chromatin condensation
3. C) activation of histone tails for enzymatic function
4. D) decreased binding of transcription factors
5. E) inactivation of the selected genes

One of her colleagues suggested she try increased methylation of C nucleotides in a

mammalian system. Which of the following results would she most likely see?

1. A) increased chromatin condensation
2. B) decreased chromatin condensation
3. C) activation of histone tails for enzymatic function
4. D) decreased binding of transcription factors
5. E) inactivation of the selected genes

A researcher introduces double-stranded RNA into a culture of mammalian cells, and can

identify its location or that of its smaller subsections experimentally, using a fluorescent probe.

In addition, she finds other evidence of this single-stranded RNA piece’s activity?

1. A) She can measure the degradation rate of the remaining single strand.
2. B) She can measure the decrease in the concentration of Dicer.
3. C) The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
4. D) The amount of miRNA is multiplied by its replication.
5. E) The cell’s translation ability is entirely shut down.

If a particular operon encodes enzymes for making an essential amino acid and is regulated
like the trp operon, then
A) the amino acid inactivates the repressor.
B) the enzymes produced are called inducible enzymes.
C) the repressor is active in the absence of the amino acid.
D) the amino acid acts as a corepressor.
E) the amino acid turns on transcription of the operon.

The functioning of enhancers is an example of
A) transcriptional control of gene expression.
B) a post-transcriptional mechanism to regulate mRNA.
C) the stimulation of translation by initiation factors.
D) post-translational control that activates certain proteins.
E) a eukaryotic equivalent of prokaryotic promoter functioning.

Which of the following is an example of post-transcriptional control of gene expression?
A) the addition of methyl groups to cytosine bases of DNA
B) the binding of transcription factors to a promoter
C) the removal of introns and alternative splicing of exons
D) the binding of RNA polymerase to transcription factors
E) the folding of DNA to form heterochromatin

What would occur if the repressor of an inducible operon were mutated so it could not bind
the operator?
A) irreversible binding of the repressor to the promoter
B) reduced transcription of the operon's genes
C) buildup of a substrate for the pathway controlled by the operon
D) continuous transcription of the operon's genes
E) overproduction of catabolite activator protein (CAP)

Which of the following statements about the DNA in one of your brain cells is true?
A) Most of the DNA codes for protein.
B) The majority of genes are likely to be transcribed.
C) Each gene lies immediately adjacent to an enhancer.
D) Many genes are grouped into operon-like clusters.
E) It is the same as the DNA in one of your kidney cells.

Which of the following would not be true of cDNA produced using human brain tissue as the
starting material?
A) It could be amplified by the polymerase chain reaction.
B) It would contain sequences representing all the genes in the genome.
C) It was produced from mRNA using reverse transcriptase.
D) It could be used as a probe to detect genes expressed in the brain.
E) It lacks the introns of the human genes.