Meiosis II and the significance of meiosis

Meiosis II starts soon after the first division and looks just like mitosis.

• Prophase II: the nuclear membrane disappears and the chromosomes become compact again.
• Metaphase II: the chromosomes line up at the equator; spindle fibres attach to the kinetochores of the sister chromatids.
• Anaphase II: the centromeres split and the sister chromatids move to opposite poles.
• Telophase II: nuclear envelopes form around each group, and cytokinesis gives a tetrad of four haploid cells.

Why meiosis matters:

• It keeps the chromosome number of each species constant from one generation to the next. Without halving, the number would double every time gametes fused.
• Through crossing over and the random sorting of chromosomes, it increases genetic variety among offspring. This variety is the raw material for evolution.

Mitosis versus meiosis, in brief: mitosis is one division that gives two diploid cells, identical to the parent. Meiosis is two divisions, with DNA copied only once, giving four haploid cells that are genetically different.