Download MEIOSIS NOTES

page 77
MEIOSIS NOTES
1/10/13
Meiosis is a form of cell division that splits the number of
chromosomes in half when forming specialized reproductive cells,
called gametes. Meiosis has two divisions of the nucleus, called meiosis I and meiosis II.
MEIOSIS I
Prophase I: The chromosomes condense, and the nuclear
envelope breaks down. Homologous chromosomes pair along
their length and then cross over.
Metaphase I: The pairs of homologous chromosomes are
moved by the spindle to the equator of the cell. The homologous
chromosomes, each made up of two chromatids, remain together.
Anaphase I: The homologous chromosomes separate. As in
mitosis, the chromosomes of each pair are pulled to opposite
poles of the cell by the spindle fibers. But in meiosis, the
chromatids do not separate at their centromeres.
Telophase I: Individual chromosomes gather at each of
the poles. In most organisms, the cytoplasm divides, forming
two new cells.
MEIOSIS II
Prophase II: Replication does not take place. Each chromosome has
two chromatids.
Metaphase II: Chromosomes line up in middle of cell, just like in Metaphase I.
Anaphase II: sister chromatids separate and move to opposite ends of
the cell.
Telophase II: The result is four haploid daughter cells, called gametes (sperm
or egg cells)
• Meiosis is a form of cell division that splits the number of chromosomes in half when forming specialized reproductive cells called gametes (also called sex cells or germ cells). • Meiosis has two divisions of the nucleus: 1. Meiosis I
2. Meiosis II
Mar 19­7:45 AM
page 77
MEIOSIS NOTES
1/10/13
MEIOSIS I
Prophase I: The chromosomes condense, and
the nuclear envelope breaks down. Homologous chromosomes pair along their length and then cross over.
Metaphase I: The pairs of homologous chromosomes are moved by the spindle fibers to the equator of the cell. The homologous chromosomes, each made up of two chromatids, remain together.
Anaphase I: The homologous chromosomes separate. As in mitosis, the chromosomes of each pair are pulled to opposite poles of the cell by the spindle fibers. But in meiosis, the chromatids do not separate at their centromeres.
Telophase I: Individual chromosomes gather at each of the poles. In most organisms, the cytoplasm divides, forming two new cells.
Mar 19­7:45 AM
1
MEIOSIS NOTES
page 77
1/10/13
MEIOSIS II
Prophase II: Replication does not take place. Each chromosome has two chromatids. Nuclear membrane disappears.
Metaphase II: Chromosomes line up in middle of cell, similar to mitosis.
Anaphase II: sister chromatids separate and move to opposite ends of the cell.
Telophase II: The result is four haploid daughter cells, called gametes (sperm or egg cells)
2
Attachments
Cornell Note Sheet for Mitosis and Meiosis.docx