Biology review Ch.15&16

How do changing patterns of gene expression in prokaryotes contribute to the organism's survival?

• Organizing gene expression so that the genes are expressed in a given order

• Allowing each gene to be expressed an equal number of times

• Allowing the organism to adjust to changes in the environmental conditions

• Allowing young organisms to respond differently than more mature organisms

The tryptophan operon in some bacteria is a repressible operon. Which of the following statements correctly describes this operon?

• It is permanently active

• It is activated only when glucose is present in the growth medium

• It is activated only when tryptophan is present in the growth medium

• It is deactivated whenever tryptophan is added to the growth medium

What would be the result of a mutation that deactivates the regulatory gene of a repressible operon in an E-coli cell?

• Continuous transcription of the enzyme coding gene controlled by that regulator

• Complete inhibition of transcription of the enzyme coding gene controlled by that regulator

• Irreversible binding of the repressor to the operator

• Inactivation of RNA polymerase by alteration of its active site

Which of the following environments would most likely lead to the transcription of the lactose operon?

• There is more glucose in the cell than lactose

• The cyclic AMP levels are low

• There is glucose but no lactose in the cell

• The cyclic AMP and lactose levels are both high within the cell

• The cAMP level is high and the lactose level is low

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?

• The repressor protein attaches to the regulator

• Allolactose binds to the repressor protein

• Allolactose binds to the operator

• Allolactose binds to the inducer

Which of the following statements correctly describes the role of DNA methylation and histone acetylation in gene regulation?

• DNA methylation reduces transcription, and histone acetylation promotes transcription

• DNA methylation promotes transcription, and histone acetylation reduces transcription

• DNA methylation and histone acetylation both promote transcription

• DNA methylation and histone acetylation both reduce transcription

Gene expression in eukaryotes can be altered by post-transcriptional processing, but this is not true for prokaryotic cells. Why not?

• Eukaryotic mRNAs get 5' caps and 3' tails, whereas prokaryotic mRNAs don't

• Prokaryotic genes are expressed as mRNA, which is more stable in the cell

• Eukaryotic exons may be spliced in alternative patterns; prokaryotic DNA does not have exons and introns

• Prokaryotes use ribosomes of different structure and size than eukaryotes

Gene expression can be blocked by a process called RNA silencing. Which of the following molecules is involved in this process?

• miRNAs

• mRNAs

• rRNAs

• tRNA

Which of the following results can a DNA microarray assay detect or identify?

• They can identify the function of any gene in a genome

• They can be used to introduce entire genomes into bacterial cells

• They can allow the expression of many or even all of the genes in a genome to be compared at once

• They allow physical maps of the genome to be assembled in a very short time

Which of the following techniques involves reverse transcriptase, PCR amplification, and gel electrophoresis?

• DNA microarray assays

• RT-PCR

• in situ hybridization

• Nucleic acid hybridization