i would like to comment on Philip's blog about how cross over takes places. he was right about how it takes places, but could have gone more in depth about it.
Crossing over takes places in prophase 1 of meiosis 1. Chromosomal crossover is the process by which two homologous chromosomes exchange portions of DNA. Crossover usually occurs when portions of homologous chromosomes brake off and rejoin with other chromosomes. This is the exchange of genes, which is called genetic recombination.
