The Sources of Genetic Diversity

It is completely random whether the maternal or paternal chromosome of each pair ends up at a particular pole. The orientation of each pair of homologous chromosomes on the metaphase plate is random, and a mixture of maternal and paternal chromosomes will be drawn toward the same cell pole by chance. This phenomenon is often called "independent assortment," and it creates new combinations of genes that are located on different chromosomes. Thus, we have two levels of gene reshuffling occurring in meiosis I. The first occurs during recombination in prophase I, which creates new combinations of genes on the same chromosome. In contrast to mitosis, the sister chromatids of a chromosome are not genetically identical because of the

anaphase II 2

anaphase II 2

telophase II

telophase II

Result: Each daughter nucleus has only half as many chromosomes as the original nucleus, and the chromosomes are not identical to those in the original nucleus.

Meiosis in an organism with six chromosomes. Replication precedes meiosis. Adapted from Curtis, 1994.

Meiosis

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