Genetics(H): Chapter 15 Practice Test(Relevant Questions)
What is the function of the terminator hairpin loop in the mRNA transcript produced by the trp operon? A) The terminator hairpin causes transcription to stop. B) The terminator hairpin loop is the binding site for the trp repressor. C) The terminator hairpin loop is the corepressor. D) The terminator hairpin loop brings tryptophan into the cell.
A
What is the role of the lacZ gene product, the enzyme beta-galactosidase? A) It converts lactose to glucose and galactose. B) It facilitates the entry of lactose into the bacterial cell. C) It removes the toxic by-products of lactose digestion from the bacterial cell. D) It converts simple sugars to lactose.
A
Which of the following is an example of positive control in operons? A) the action of the catabolite activator protein (CAP) in the lac operon B) regulation of the lac operon by the lac repressor C) the regulation of the tryptophan operon by the trp repressor D) attenuation of the trp operon
A
Which of the following statements best describes the trp operon? A) It is repressible and under negative control. B) It is repressible and under positive control. C) It is inducible and under positive control. D) It is inducible and under negative control.
A
Which term is used to describe enzymes that are produced only when specific substrates are present in the environment? A) inducible B) negatively controlled C) constitutive D) repressible
A
sRNAs have been shown to play important roles in gene regulation in response to changing environmental conditions. A) True B) False
A
Why are genes related to common functions found together in operons? A) for the correct function of the operon even if some genes are mutated B) for coordinated responses C) for inhibition of undesirable processes D) for fast regulation of metabolic needs
B
What advantages do regulatory systems provide to bacteria? A) enable bacteria to function normally in the absence of nutrient medium B) able transcription of different genes in different environments C) provide an efficient response to protect bacteria from harmful environmental factors D) ability to turn off metabolic functions when they are not needed E) allow the necessary mutations of bacterial genes for adaptation of bacteria in different environments
C
What is a riboswitch? A) inhibition of transcription based upon binding of a regulatory protein to the operator B) a regulatory protein that binds to the promoter C) a form of gene regulation based on secondary structure of mRNA sequences present in the 5'UTR D) promotion of transcription based upon binding of a regulatory protein to the promoter
C
Which statement regarding small noncoding RNAs (sRNAs) is false? A) sRNAs can block translation by masking the ribosome-binding site (RBS). B) sRNAs regulate gene expression by binding to mRNAs, usually at the 5'-end. C) sRNAs are always negative regulators of gene expression. D) sRNAs are often transcribed from loci that partially overlap the coding regions of the genes they regulate.
C
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