Answer: Crossing over (genetic recombination) in Prophase I.
- A Sites of further chromosome condensation in metaphase
- B Crossing over (genetic recombination) in Prophase I
- C Points of spindle microtubule attachment to kinetochores
- D Sites of nuclear envelope breakdown in prophase
Correct answer: B. Crossing over (genetic recombination) in Prophase I
Explanation: Chiasmata are the X-shaped crossing points where homologous chromosomes have exchanged DNA. They hold bivalents together.
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.