Lytic and lysogenic cycles Knowledge-Based Download PDF

Questions

1. 1.

   During the early phase of the lytic cycle, a bacteriophage directs the degradation of the host bacterium's chromosome. What is the primary biological purpose of this event for the virus?

   • A) It shuts down host gene expression and provides nucleotides for viral genome replication.
   • B) It promotes the integration of the viral genome into vacant chromosomal regions.
   • C) It stimulates the host cell to divide rapidly before viral assembly can begin.
   • D) It activates host DNA repair enzymes necessary for translating capsid proteins.
2. 2.

   In the lysogenic cycle of a temperate bacteriophage, how is the viral genome propagated to new bacterial cells?

   • A) It is replicated along with the host chromosome by the host bacterium's DNA replication machinery during binary fission.
   • B) It is amplified independently by viral DNA polymerases while the host cell chromosome is fragmented and degraded.
   • C) It is packaged into newly assembled virions that are released through cell lysis to infect adjacent daughter cells.
   • D) It is transcribed into double-stranded RNA intermediates that replicate autonomously in the bacterial cytoplasm.
3. 3.

   During the lytic cycle of a virulent bacteriophage, which step occurs immediately after the biosynthesis of viral nucleic acids and viral proteins?

   • A) Assembly of newly synthesized components into mature virions
   • B) Enzymatic breakdown and lysis of the host bacterial cell wall
   • C) Injection of viral genetic material into the host cytoplasm
   • D) Integration of the viral genome into the bacterial chromosome
4. 4.

   Under environmental stress such as ultraviolet radiation-induced DNA damage, which event causes a temperate bacteriophage to switch from the lysogenic cycle to the lytic cycle?

   • A) Immediate integration of circularized viral DNA into host plasmids
   • B) Enzymatic degradation of existing viral capsids by host proteases
   • C) Induction, leading to the excision of the prophage from the host chromosome
   • D) Permanent inactivation of viral promoters by bacterial histone-like proteins
5. 5.

   Which of the following events uniquely characterizes the lysogenic cycle of a bacteriophage rather than its lytic cycle?

   • A) Rapid degradation of the host chromosome upon entry
   • B) Immediate synthesis of viral capsid proteins
   • C) Integration of the viral genome into the host cell chromosome as a prophage
   • D) Lysis of the host bacterium to release newly assembled virions