Crossing over is the exchange of chromosomal segments between non-sister chromatids of homologous chromosomes during the production of gametes. It occurs during pachytene stage. (Ref. to Fig. 28.4) 
Crossing over that results in genetic recombination in higher organisms occurs between:
Held on 30 Apr 2004 · Verified 9 Jul 2026.
sister chromatids of a bivalent
non-sister chromatids of a bivalent
two daughter nuclei
two different bivalents.
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