Meiosis

Meiosis

• The process of Meiosis has TWO divisions• In the end of the FIRST division, one cell

divides into two• In the SECOND division, two cells divide into

four

• So you start with 1 cell and the end result is 4 cells!

Gamete Cells

• The second division in meiosis produces gamete cells

• Gamete cells are sex cells• These cells have HALF of the number of

chromosomes the original cell had

Haploid/Diploid

• The original cell at the beginning of Meiosis is a diploid cell

• Di- means TWO• Diploid cells have 2 sets of chromosomes• Haploid cells only have 1 set• The result of meiosis is 4 HAPLOID CELLS• These haploid cells are used in reproduction

Meiosis – FIRST DIVISION

• In phase 1 (prophase 1) – chromosomes (each consist of 2 chromatids) condense – crossing over can occur

• In phase 2 (metaphase 1) – homologous chromosomes align in the center of the cell

• In phase 3 (anaphase 1) – chromosomes separate with sister chromatids still together

• In phase 4 (telophase 1) – cell pinches into two cells each containing 1 chromosome of the homologous pair

http://www-bcf.usc.edu/~forsburg/meiosis.html

Meiosis – SECOND DIVISION

• In phase 1 (prophase 2) – chromosomes condense

• In phase 2 (metaphase 2) – chromosomes line up in the center of the cell

• In phase 3 (anaphase 2) – sister chromatids separate and move to opposite ends of the cells

• In phase 4 (telophase 2) – two cells pinch into 4 cells

Adapted from http://www-bcf.usc.edu/~forsburg/meiosis.html

Taken from http://www.infovisual.info/01/021_en.html

Take a look at the both stages together