Unit 6 Ch 17

A repressible operon in bacteria codes for the genes required to produce the amino acid serine. Serine functions as a corepressor for the operon. If serine is present in the bacteria's environment, which of the following is most likely?

• increased digestion of serine

• increase in the levels of serine

• increased production of the repressor protein

• increased binding of the repressor protein to the operator

The arabinose operon is an inducible operon that codes for the genes required to digest the sugar arabinose. Arabinose functions as an inducer molecule for the operon. If arabinose is present in the bacteria's environment, which of the following is most likely?

• increased digestion of arabinose

• increase in the levels of arabinose

• increased production of the repressor protein

• increased binding of the repressor protein to the operator

Which sequences in bacterial operons are noncoding sequences?

• operators and promoters only

• operators, promoters, and genes for regulatory proteins

• operators, promoters, and genes for structural proteins

• promoters, genes for regulatory proteins, and genes for structural proteins

Which of the following is a key difference between inducible operons and repressible operons?

• Inducible operons have promoter sequences, and repressible operons do not have promoter sequences.

• Inducible operons have operator sequences, and repressible operons do not have operator sequences.

• The repressor in an inducible operon can bind to the operator sequence on its own, but the repressor in a repressible operon requires a corepressor in order to bind to the operator.

• In inducible operons, RNA polymerase requires the presence of a corepressor in order to bind to the promoter; in repressible operons, RNA polymerase does not require a corepressor.

Under which of the following conditions will transcription of the lac operon be at its highest level?

• low glucose, low lactose

• low glucose, high lactose

• high glucose, low lactose

• high glucose, high lactose

Adding a methyl group to a DNA nucleotide is a type of (a)   and will make a DNA sequence much less likely to be transcribed.

Which of the following are proteins in eukaryotes that bind to regulatory switches and upregulate gene expression?

• activators

• repressors

• transcription factors

• mediators

Not every change in the DNA sequence results in a change in the amino acid sequence of a protein. Which of the following explains this?

• Each organism lives in a different environment, which changes the expression of its genes.

• The genetic code is redundant, and more than one codon codes for most amino acids.

• The proofreading function of ribosomes corrects changes in the DNA sequence.

• Differential gene expression adapts to these changes in the DNA sequence.

Which of the following methods of horizontal transmission of genetic material would be most likely to lead to new variants of the COVID-19 virus?

• transformation

• transduction

• transposition

• conjugation

Which of the following does not affect the phenotype of an organism?

• the genes that are expressed

• the level at which genes are expressed

• the timing of gene expression

• the number of genes in the organism