Quiz on Operons and Gene Expression

What is an operon, and why is it important in gene expression in prokaryotes?

• A type of protein required for gene transcription.

• A sequence of DNA that codes for regulatory proteins.

• A group of genes that function together in the same biochemical pathway and are regulated as a unit.

• A promoter sequence for RNA polymerase binding.

In the E. coli lac operon, what is the role of IPTG (isopropylthiogalactoside)?

• It acts as a substrate for lactose metabolism.

• It serves as a repressor that blocks gene expression.

• It mimics lactose but is not metabolized, inducing the operon.

• It inhibits RNA polymerase activity.

What does the attenuation mechanism in the trp operon involve?

• It uses a repressor protein to inhibit transcription.

• It forms stem-loop structures in mRNA to regulate transcription based on tryptophan levels.

• It involves the degradation of tryptophan when levels are high.

• It activates translation when tryptophan is present.

Why is the Shine-Dalgarno sequence important for translation initiation?

• It prevents translation by binding to the start codon.

• It facilitates the binding of the ribosome to mRNA for translation.

• It serves as a termination signal for translation.

• It codes for the start of protein synthesis.

Which of the following is a primary reason for plasmid instability in prokaryotic cells?

• Low levels of tryptophan.

• Inefficient translation initiation due to an incorrect SD sequence.

• Segregational loss during cell division.

• High copy number of plasmids.