Molecular Biology Quiz

Which of the following molecules is a protein produced by a regulatory gene?

• operon

• inducer

• promoter

• repressor

Which of the following molecules helps to "turn off" genes in a cell?

• operon

• inducer

• promoter

• corepressor

When taken up by a cell, which of the following molecules binds to a repressor so that the repressor no longer binds to the operator?

• inducer

• promoter

• repressor

• corepressor

Most repressor proteins are allosteric. Which of the following molecules binds with the repressor to alter its conformation and therefore affect its function?

• inducer

• promoter

• transcription factor

• cAMP

Which of the following processes would result from a mutation that deactivates a regulatory gene of a repressible operon in an E. coli cell?

• A) continuous transcription of the structural gene controlled by that regulator

• B) complete inhibition of transcription of the structural gene controlled by that regulator

• C) irreversible binding of the repressor to the operator

• D) continuous translation of the mRNA because of alteration of its structure

Which of the following conditions is most likely to cause the lactose operon to be transcribed?

• A) There is more glucose in the cell than lactose.

• B) There is glucose but no lactose in the cell.

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

• D) The cAMP level is high and the lactose level is low.

How does the transcription of structural genes in an inducible operon occur?

• A) It occurs continuously in the cell.

• B) It starts when the pathway's substrate is present.

• C) It starts when the pathway's product is present.

• D) It stops when the pathway's product is present.

For a repressible operon to be transcribed, which of the following conditions must occur?

• A corepressor must be present.

• RNA polymerase and the active repressor must be present.

• RNA polymerase must bind to the promoter, and the repressor must be inactive.

• RNA polymerase must not occupy the promoter, and the repressor must be inactive.

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by ________.

• organizing gene expression, so that genes are expressed in a given order

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

• allowing an organism to adjust to changes in environmental conditions

• allowing environmental changes to alter a prokaryote's genome

In positive control of several sugar metabolism-related operons, the cAMP receptor protein (CRP) binds to DNA to stimulate transcription. Which of the following environmental conditions causes an increase in CRP activity in stimulating transcription?

• an increase in glucose and an increase in cAMP

• a decrease in glucose and an increase in cAMP

• an increase in glucose and a decrease in cAMP

• a decrease in glucose and a decrease in the repressor