What is the key event that occurs at the onset of anaphase?

What is the key event that occurs at the onset of anaphase?
  1. Chromosomes are moved to spindle equator
  2. Centromeres split and chromatids separate
  3. Chromosomes are aligned along metaphase plate
  4. Spindle fibres attach to kinetochores of chromosomes

Solution

At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as daughter chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles.

Asked in: NCERT

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