Exam 17: Regulation of Gene Expression in Bacteria and Bacteriophages

For each of the following lac operon mutations,state whether transcription of β-galactosidase will increase,decrease,or be unaffected. a.P_lac^- b.lacY⁺ c.lacI^- d.lacO^- e.lacA^-

To inhibit the transcription of operon genes,the lacI gene product binds to

The structural genes in the lac operon are transcribed into a single polycistronic mRNA molecule.

Mutants that are lacI^S do not produce lac enzymes,regardless of the presence or absence of lactose.

Operons can best be defined as

The purpose of regulation of the trp operon in bacteria is to ensure the cell can digest tryptophan if it is present and the cell is short on energy.

During transcription of the trp operon,pairing of regions 2 and 3 in the leader peptide mRNA creates a(n)________ signal.

Which of the following can be a transdominant mutation in partial diploid cells?

lacI^S encodes superrepressors,repressors that always bind to the operator and prevent gene transcription.

Microbial genomics is a rapidly growing field.Of great interest to geneticists is the search for new operons as new microbial genome sequences become available.What kind of "signature" or identifying feature would you look for as you searched new genomes for candidate operons?

How are partial diploid E.coli constructs made?

Should viruses like lambda phage be considered living entities? Or are they more properly viewed as parasitic fragments of DNA?

Distinguish between cis- and trans-dominance.

If a cell has the partial diploid genotype $\mathrm { lacI } ^ { + } \quad \operatorname { lacO } ^ { - } \operatorname { lac } ^ { + } \quad \operatorname { lac } ^ { + }$ $\overline { l a c I ^ { - } l a c O ^ { - } ~ l a c Z ^ { + } \operatorname { lac } Y ^ { - } }$ , how will its gene expression function in the presence of allolactose?

If a cell has the partial diploid genotype how will its gene expression in the presence of allolactose?

The genetic switch for the infection pathways of lambda phage is controlled by two regulatory proteins: ________ and ________.

The ________ pathway in lambda phage leads to integration of viral DNA with that of the host,while the ________ pathway leads to induction of progeny viruses.

The tryptophan codons of the attenuator sequence help speed up transcription of downstream trp genes at high concentrations of tryptophan.

Which of the following mutations is dominant over wild-type lacI⁺ in a partial diploid experimental cell?