Q.67 Which one of the following phages undergoes non-integrative lysogenic phase?
(A) 𝜆
(B) P 1
(C) T 7
(D) M13

Which Phage Undergoes Non-Integrative Lysogenic Phase? 

P1 phage is the correct answer as it maintains its genome as a plasmid during lysogeny without chromosomal integration. This multiple-choice question tests understanding of bacteriophage life cycles in microbiology.​

Correct Answer

(B) P1
P1 forms a low-copy plasmid that replicates autonomously and partitions during cell division.​

Lambda Phage (𝜆) Explanation

Lambda phage is a temperate phage that integrates its genome into the E. coli chromosome as a prophage during lysogeny. The cI repressor protein maintains this integrated state by blocking lytic genes.​

P1 Phage Details

P1 phage enters lysogeny without integrating into the host genome; instead, its 90 kb DNA circularizes and functions as a plasmid. This non-integrative mechanism allows stable maintenance through plasmid partitioning during bacterial division.​

T7 Phage Cycle

T7 is an obligately lytic phage that replicates rapidly in E. coli, producing many progeny before host lysis. It lacks a lysogenic phase entirely.​

M13 Phage Characteristics

M13 is a filamentous phage that establishes chronic infection without lysogeny or cell lysis. It extrudes single-stranded DNA particles continuously from living hosts.​