What is the name for the recombination process that occurs between long homologous DNA sequences and drives accurate exchange?
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AMutagenic recombination
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BSite-specific recombination
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CReplicative recombination
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DGeneral (homologous) recombination
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EIllegitimate recombination
Answer
Correct Answer: General (homologous) recombination
Explanation
Introduction / Context:Cells exchange DNA via distinct recombination mechanisms. Homologous recombination underlies faithful DNA repair, meiotic crossing-over, and integration of very similar sequences. Recognizing the correct category is essential in genetics and biotechnology.
Given Data / Assumptions:
- Sequences involved are homologous (high sequence identity).
- Proteins such as RecA/Rad51 catalyze strand invasion and exchange.
- Outcome is accurate exchange with minimal sequence alteration.
Concept / Approach:General (homologous) recombination aligns matching sequences and swaps strands through a Holliday junction intermediate, ensuring precise crossover. Site-specific recombination uses dedicated recombinases at short recognition sites (for example, att); replicative recombination can describe transposition mechanisms; mutagenic/illegitimate recombination does not require long homology and is error-prone.
Step-by-Step Solution:Identify hallmark: long stretches of homology dictate the mechanism.Associate with RecA/Rad51 and Holliday structures.Select “general (homologous) recombination.”
Verification / Alternative check:Experimental genetic mapping in bacteria and meiosis in eukaryotes both demonstrate homologous recombination frequency depends on sequence identity and distance between markers.
Why Other Options Are Wrong:
- Site-specific: needs unique short sites, not long homology.
- Replicative: often refers to transposon copy-in events.
- Mutagenic/illegitimate: non-homologous, error-prone.
Common Pitfalls:Equating any recombination with homologous; mechanisms are specialized and context-dependent.
Final Answer:General (homologous) recombination