Answer: A four-way DNA junction formed during crossing-over (resolved to form crossover or non-crossover products).
- A A specific site along the chromosome where double-strand breaks occur before any strand invasion or branch migration ever takes place there
- B A four-way DNA junction formed during crossing-over (resolved to form crossover or non-crossover products)
- C A multi-subunit protein complex that mediates chromosome cohesion composed of cohesin subunits rather than any recombining DNA strands
- D A chromatin modification that marks regions destined for recombination deposited well before meiosis begins, unrelated to active strand exchange
Correct answer: B. A four-way DNA junction formed during crossing-over (resolved to form crossover or non-crossover products)
Explanation: Holliday junction: four-stranded structure formed by branch migration during recombination. Resolution by resolvases determines if crossover (CO) or non-crossover (NCO) outcome.
The cell cycle: G1 (growth and preparation), S (DNA replication, chromosome number stays 2n but DNA content doubles), G2 (final checks before division), and M (mitosis itself) - together, G1+S+G2 make up interphase.
Concept context
Mitosis and meiosis: how cells divide for growth, repair, and reproduction.