Bio 112 Chapter 18

Which of the following levels of gene expression allows the most rapid response to environmental change?

• Transcriptional control

• Translational control

• Post-translational control

• None of the above

2) Bacterial and eukaryotic cells primarily control gene expression at the level of transcription. If

instead cells exerted control of gene expression primarily at the post-translational level, what

would be different?

• The ability to rapidly respond to environmental change would be reduced.

• Cells would expend significantly more energy.

• Genes would no longer be transcribed.

• Translation of mRNA into protein would not occur.

Which of the following genes would you predict to be constitutively (constantly) expressed?

• Genes involved in the biosynthesis of the amino acid tryptophan

• Genes involved in the degradation of tryptophan

• Genes involved in the degradation of arabinose, a sugar

• Genes that code for regulatory proteins

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 young organisms to respond differently than more mature organisms

The greatest expression of the lac operon occurs when lactose levels are _______.

• low and glucose levels are low

• low and glucose levels are high

• high and glucose levels are low

• high and glucose levels are high

X-gal is widely used in molecular genetic research and is chemically similar to _______.

• glucose

• galactose

• lactose

• a compound that can only be transported into lacZ mutants

In negative control, a gene is switched off when ________.

• a kinase adds a phosphate to DNA

• lactose is transported into the cell

• a regulatory protein binds to DNA and shuts down transcription

• a regulatory protein is removed from DNA and shuts down transcription

The product of the lacI gene functions most like a car's ________.

• parking brake

• accelerator pedal

• steering wheel

• engine

• gear shift

The product of the lacI gene is ________.

• an enzyme

• a transport protein embedded within the membrane

• β-galactosidase

• the repressor

10) An E. coli cell without a functional lacI gene is expected to ________.

• Never produce β-galactosidase

• Always produce β-galactosidase

• Be unable to transport lactose into the cell

• Be unable to metabolize lactose within the cell