Bacteriophage Replication and Gene Regulation

Vocabulary flashcards covering viral replication mechanisms, phage phi X proteins, and genetic regulatory elements of temperate phage lambda.

Protein E (phi X)

A passive release protein encoded by phi X that blocks host cell wall synthesis, causing the host cell wall to fail and rupture over time.

Burst size

The average number of complete, infectious viral particles produced per host cell by the time cell burst or lysis occurs.

Protein A (phi X)

A phi X protein required for viral single-stranded and double-stranded genome replication.

Protein C (phi X)

A phi X protein responsible for linking viral genome replication with capsid construction.

Temperate phage

A virus, such as phage lambda, capable of carrying out either lytic replication or lysogenic replication.

Prophage

The state of viral existence where phage genetic information resides inside the host (often integrated into the host chromosome) without expressing full lytic particle production.

Lysogen

A bacterial host cell that contains a prophage within its genome.

Induction

The event, typically triggered by host DNA damage, that leads to derepression and transitions a phage from lysogeny into the lytic cycle.

PL (Promoter of leftward transcription)

An immediate early promoter in phage lambda that controls leftward transcription of genes starting with the N gene.

PR (Promoter of rightward transcription)

An immediate early promoter in phage lambda that controls rightward transcription of genes starting with the cro gene.

N protein

An anti-terminator protein in phage lambda that interacts with host RNA polymerase to bypass early terminators and extend transcription leftward and rightward.

cro protein

A repressor protein encoded by phage lambda that binds operator sequences (highest affinity for operator 3) to shut off c1 expression and promote lytic gene expression.

Q protein

An anti-terminator protein in phage lambda that acts rightward to enable transcription of late genes involved in the lytic pathway.

c2 protein

A promoter enhancer protein in phage lambda that activates transcription from promoters Pint, PAQ, and PRE.

c1 protein

A repressor protein in phage lambda that binds operator sequences (highest affinity for operator 1, followed by operator 2) to shut off lytic promoters and maintain lysogeny via PRM.

PRE (Promoter of repressor establishment)

A promoter activated by c2 that directs the initial leftward transcription of c1 to establish lysogeny.

PRM (Promoter of repressor maintenance)

A promoter in phage lambda that controls self-sustained leftward expression of c1 after c1 binds operator 2.

Pint

A promoter activated by c2 that drives the transcription of the integrase gene required for integrating phage DNA into the host genome.

PAQ

A promoter activated by c2 that produces an antisense transcript complementary to Q mRNA, blocking translation of Q to delay lytic development.

Operator

A specific DNA sequence embedded in or near a promoter to which regulatory repressor proteins (such as c1 or cro) bind to regulate transcription.