Rephrasing question: does crossover happen after sperm and egg meet each other, but before formed fetus starts to grow?

As I understand sperm and egg of human are haploid cells. That means this cells undergone meiosis and chromosomes crossover before meet each other. If so then crossover happened between a pair of chromosomes which came from parents of the parent of the fetus, not between chromosomes of mother and father of the fetus.

Am I wrong?

  • $\begingroup$ No, you are right. $\endgroup$
    – Roni Saiba
    Jul 19, 2017 at 1:29

1 Answer 1


Your question and your rephrased question aren't asking the same thing, so you may want to edit your question.

Crossover occurs during meiosis, which is a type of cell division that occurs in the generation of gametes, during which of course only the chromosomes from one of the eventual parents would be present. Meiosis doesn't occur in the fetus, except eventually in the germ line cells.

  • $\begingroup$ Thanks for answer. So crossover happen before sperm and egg cells meet each other, right? $\endgroup$
    – Kos
    Jul 19, 2017 at 16:22
  • $\begingroup$ @wandalen Yes: it occurs when the progenitors of those cells divide to produce gametes. $\endgroup$
    – Bryan Krause
    Jul 19, 2017 at 16:23

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