A2.3.3 (HL)—Lytic cycle
In the lytic cycle, lambda phage DNA remains separate from bacterial DNA, directs production and assembly of new virions, and ends by lysing the host.
- Syllabus
- First assessment 2025
- Objective
- A2.3.3
- Level
- HL
Exam analysis
Chance of appearing2%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1A
Typical marks1–3
Common command terms
- Identify
- Compare
- Contrast
Scoring notes
- Common mistake
- Reversing the cycles by placing viral DNA integration in the lytic cycle.
Recent exam appearances
November 2025Paper1B ["HL"] · TZ31(d)[ 3 ]A2.3.3 (HL)—Lytic cycle
May 2025Paper1A ["HL"] · TZ313[ 1 ]A2.3.3 (HL)—Lytic cycle
Practice this objective
Coverage 2025–2025 · Updated 15 Jul 2026
Concept essentials
- Lambda phage attaches to E. coli and injects its DNA into the host.
- Lytic viral DNA remains separate from the bacterial chromosome.
- Host machinery produces viral DNA and proteins that assemble into new phages.
- The lytic cycle ends with bacterial cell lysis and virion release.