Crossing over involves the exchange of corresponding segments between

  • A. two sister chromatids of the same chromosome
  • B. any two chromatids chosen at random
  • C. the two strands of one DNA molecule
  • D. non sister chromatids of homologous chromosomes

Explanation

Exchange between non sister chromatids of homologues shuffles maternal and paternal alleles, creating recombinant gametes. Exchange between sister chromatids would swap identical material and produce nothing new.

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