Regulation of Gene Expression in Prokaryotes and Eukaryotes

Which level is not a potential point of regulation of gene expression?

• The level of transcription

• The level of processing mRNA

• The level of mRNA stability

• The level of translationt

• The level of protein export

Which statement about transcription factors is true?

• All transcription factors are repressors

• All transcription factors are activators.

• A promoter is a transcription factor.

• A transcription factor can be an activator or a repressor.

• A transcription factor can be both an activator and a repressor.

A transcription factor is a _______ that binds to _______.

• protein; DNA

• protein; RNA

• promoter; a protein

• gene; DNA

• gene; RNA

In which of these pairs do the two entities act in opposite ways?

• A constitutive gene and an activator

• A transcription factor and a constitutive gene

• A repressor and an activator

• A promoter and a repressor

• e. A promoter and an activator

In negative regulation

• the gene is never transcribed.

• the gene is always transcribed.

• the binding of an activator stimulates transcription.

• transcription can be turned off when a repressor binds to the DNA near the promoter.

• a transcription factor is required in order for the gene to be transcribed. Answer

An inducer

• inhibits the synthesis of needed enzyme(s).

• stimulates the synthesis of needed enzyme(s).

• binds to the promoter and prevents the repressor from binding to the operator.

• binds to the operator and prevents the repressor from binding at this site.

• binds to the termination codons and allows protein synthesis to continue.

Actin, a protein found in almost all eukaryotic cells, is expressed in most cell types at a fairly constant level. Thus, the gene that codes for actin can be considered a(n) _______ gene.

• inducible

• activated

• repressible

• constitutive

• transcription factor

The lac operon of E. coli consists of

• a promoter and an operator.

• an operator and three structural genes.

• three structural genes and a promoter.

• a promoter, an operator, and three structural genes.

• a promoter, a director, and two structural genes.

Which statement about operons is false?

• The structural genes in the operon are either all on or all off at a given time.

• They consist of a cluster of genes with a single promoter.

• Their DNA is transcribed into a single molecule of mRNA.

• They are the units of transcriptional regulation in prokaryotes.

• A repressible operon is turned off unless needed.

How are inducible and repressible systems similar?

• Both systems control primarily catabolic pathways.

• In both systems, the final product of the pathway usually regulates transcription of the genes that will encode enzymes that produce it.

• In both systems, the regulatory molecules function by binding to the operator.

• Blocking transcription is the default state for both systems.

• Both systems control primarily anabolic pathways.