Q.54 The lytic cycle of Phage T4 has

1. Self-assemble of three different protein to form phage component.
2. T4 makes attachment with specific surface protein through tail fibres.
3. Production of enzyme to damage bacterial cell wall.
4. Contraction of tail sheath, DNA enters into the cell leaving capsid outside.
5. Phage DNA directs production of phage protein and copies of phage genome with the help of host and viral enzyme.

Choose the correct answer from the options given below :

1. B, C, D, E, A
2. B, D, A, E, C
3. B, D, E, A, C
4. B, C, A, D, E

   Phage T4 follows a lytic cycle where it attaches to the host, penetrates, replicates, assembles, and lyses the cell, with the correct step order being B, D, E, A, C.​

   Step Explanations

   T4 attachment via tail fibres (B) initiates infection by binding specific bacterial surface proteins. Tail sheath contraction (D) follows, injecting DNA while leaving the empty capsid outside. Phage DNA directs protein/genome production (E) uses host and viral enzymes for replication and synthesis. Self-assembly of phage proteins (A) forms new virions from components. Finally, lytic enzyme production (C) degrades the cell wall for release.

   Option Analysis

   • B, C, D, E, A: Incorrect; enzyme production (C, lysis) too early before replication/assembly.

   • B, D, A, E, C: Incorrect; assembly (A) before replication (E) lacks components.

   • B, D, E, A, C: Correct; standard sequence: attachment, penetration, biosynthesis, assembly, lysis.

   • B, C, A, D, E: Incorrect; lysis enzyme (C) and assembly (A) out of order, before DNA entry.

   Introduction to Phage T4 Lytic Cycle Steps

   The Phage T4 lytic cycle steps outline how this bacteriophage infects E. coli, replicates destructively, and releases progeny, crucial for GATE Life Sciences microbiology prep. It proceeds via attachment, penetration, biosynthesis, assembly, and lysis in ~30 minutes at 37°C.

   Detailed Phage T4 Lytic Cycle Steps

   Key steps match the query:

   • Attachment with tail fibres (B): Binds specific bacterial receptors.​

   • Tail sheath contraction, DNA entry (D): Injects genome, capsid remains outside.​

   • Phage DNA directs production (E): Replicates genome, synthesizes proteins using host machinery.​

   • Self-assembly of proteins (A): Forms ~150 new phages.​

   • Enzyme damages cell wall (C): Lysozyme causes lysis for release.​

   Step Label	Description	Stage	Purpose
   B	Tail fibres attachment	Adsorption	Specific binding ​
   D	Sheath contraction, DNA entry	Penetration	Genome injection ​
   E	DNA directs phage production	Biosynthesis	Replication/synthesis ​
   A	Protein self-assembly	Maturation	Virion formation ​
   C	Enzyme for cell wall damage	Release	Progeny escape ​

   GATE Q.54 Solution

   Correct order for Phage T4 lytic cycle is B, D, E, A, C, aligning with classic stages without premature lysis or assembly. Invalid options disrupt replication timing.​