MEIOSIS

MEIOSIS
          - type of cell division involving reproductive cells

Phases

Meiosis I
     stages:

Prophase I

• two sister chromatids of each chromosome pair up with the chromatids of its homologue (synapsis)
• makes up 90% of the entire process
• forms a structure called tetrads
• chromatids of homologous chromosomes exchange segments (crossing-over)
• nucleoli and nuclear membrane start to disappear

Metaphase I

• homologous chromosomes align at the middle of the cell

Anaphase I

• movement of the chromosomes of each homologous pair toward the opposite poles of the cell
• individual chromosome still consist of two sister chromatids

Telophase I and Cytokinesis

• chromosomes are on each side of the pole
• chromosome still consist of two sister chromatids
• nucleoli and nuclear membrane reappear

Meiosis II
     stages:

Prophase II

• starts with haploid cells
• nuclear envelope starts to breakdown

Metaphase II

• chromosomes line up along the cell equator

Anaphase II

• chromosomes are pulled toward the opposite poles of the cell

Telophase II

• chromosomes finish their migration to poles
• nuclear membrane forms again and nucleolus reappear

Cytokinesis

• four new daughter cells are produced, each with a haploid number of chromosomes