More info about crossing-over: http://www.biology.demon.co.uk/Biology/mod2/mitosis/chiasma.htm

A text summary of the clickable map above, meant for web-crawlers and other automatic tools:
crossing-over occurs at site tetrad
crossing-over process included in meiosis
crossing-over process included in early prophase I
crossing-over has result new genetic recombinations
crossing-over includes process breaking/rejoining chromosomes
crossing-over includes process exchange of genetic material