Genetic recombination mechanisms: Which type of recombination does not require long homologous sequences and is used for integration of viral genomes into bacterial chromosomes (for example, phage integration)?

Introduction / Context:Cells and viruses use different recombination strategies. While homologous recombination needs extended sequence identity, some biological integrations occur at short consensus sites with dedicated recombinases, a hallmark of viral integration and many mobile elements.

Given Data / Assumptions:

• The question highlights integration of viral DNA into the bacterial chromosome.
• Phage lambda integrates at att sites using integrase and excisionase.
• Minimal homology is required—short, specific motifs are sufficient.

Concept / Approach:

Site-specific recombination uses recombinases that recognize short sequence motifs present on both the circular viral genome and the host chromosome. The reaction is precise and does not depend on RecA-mediated extensive homology.

Step-by-Step Solution:

Verification / Alternative check:

Integrase family recombinases (e.g., tyrosine or serine recombinases) mediate integration and excision with short site specificity, consistent with the question.

Why Other Options Are Wrong:

General recombination: requires extensive homology and RecA.

Replicative recombination: describes transposition mechanisms where DNA is duplicated during movement.

“Mutagenic recombination”: not a standard category describing phage integration.

Common Pitfalls:

Equating any recombination with homologous recombination; integration is often site-specific and enzyme-directed.

Final Answer:

Site-specific recombination