The Events of Meiosis

1. Homologous chromosomes pair up.
   • Condensation of chromatin occurs, chromosomes appear as packets of four chromatids, and nonsister chromatids exchange segments in a process called crossing over.
   • Because alleles for the same trait can vary, new combinations of genes in each chromosome can result. This is one source of genetic variation.
2. Crossing over leads to genetic recombination.

Metaphase I:

During metaphase I , homologous chromosomes randomly line up at the spindle equator. Maternal and paternal chromosomes are shuffled most during metaphase I. Spindle fibers attach to the centromere region of each homologous chromosome pair.

Anaphase I:

During anaphase I, homologous chromosomes (still duplicated) separate and are drawn to opposite poles by the spindle fibers. This results in the formation of two haploid cells, each of which has a random mix of maternal and paternal chromosomes.

Telophase I:

Telophase I is similar to Telophase of mitosis, except that only one set of (replicated) chromosomes is in each "cell". Each of the cells formed during Telophase I is haploid.

Prophase II:

In prophase II the spindle fibers reform.

Metaphase II:

Metaphase II is similar to mitosis, with spindles moving chromosomes into the equatorial area and attaching to the opposite sides of the centromeres.

Anaphase II:

During Anaphase II, the centromeres split and the former chromatids (now chromosomes) are segregated into opposite sides of the cell.

Telophase II:

Telophase II is similar to Telophase of mitosis. Cytokinesis separates the cells.

This animation (Audio - Important) describes the events of meiosis.

This tutorial is a good review of (Audio - Important) meiosis.

REVIEW: Pairing of homologues and crossing over occur during
Answer prophase I.