Meiosis occurs in a series of different phases and creates genetically unique reproductive cells. The steps of meiosis are shown. Which process helps make meiotic cells genetically different and occurs during prophase I, but not during prophase II?

Crossing-over

Explanation:

Meiosis is a kind of cell division that occurs only in sexually-reproducing organisms. It is the process by which they produce gametes. Meiosis is that division in which the number of chromosomes in the resulting cells are reduced by half. Due to this reason, meiosis occurs in a two step division process viz: Meiosis I and II.

Meiosis produces genetically different reproductive cells. This is as a result of a phenomenon unique to only meiosis called CROSSING-OVER. Crossing-over is a process whereby non-sister chromatids of homologous chromosomes exchange a segment of their genetic material. It occurs only in Prophase 1 of meiosis where the TETRAD structure is formed. This exchange of genetic material causes a recombination of DNA in the resulting cell (gamete).

Crossing-over only occurs between non-sister chromatids of homologous chromosomes, hence, it can only occur in Prophase 1. Prophase II involves sister chromatids.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.