Meiosis
Legend:
Illustration of the process by which a single parent diploid cell
(Both homologous chromosomes) divides to produce four daughter haploids
cells (One homologous chromosome of the pair).
Meiosis is the type of cell division by which germ cells (eggs
and sperm) are produced. Meiosis involves a reduction in the amount of genetic
material.
Meiosis comprises two successive nuclear divisions with only one round
of DNA replication.
Four stages can be described for each nuclear division.
- Interphase: Before meiosis begins, genetic material is duplicated.
- First division of meiosis
- Prophase 1: Duplicated chromatin condenses. Each chromosome consists of two, closely associated sister chromatids. Crossing-over can occur during the latter part of this stage.
- Metaphase 1: Homologous chromosomes align at the equatorial
plate.
- Anaphase 1: Homologous pairs separate with sister chromatids
remaining together.
- Telophase 1: Two daughter cells are formed with each daughter
containing only one chromosome of the homologous pair.
- Second division of meiosis: Gamete formation
- Prophase 2: DNA does not replicate.
- Metaphase 2: Chromosomes align at the equatorial plate.
- Anaphase 2: Centromeres divide and sister chromatids migrate
separately to each pole.
- Telophase 2: Cell division is complete. Four haploid daughter
cells are obtained.
One parent cell produces four daughter cells. Daughter cells have half
the number of chromosomes found in the original parent cell and with crossing
over, are genetically different.
Meiosis differs from mitosis primarily
because there are two cell divisions in meiosis, resulting in cells with
a haploid number of chromosomes.
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