MITOSIS, CYTOKINESIS, MEIOSIS AND APOPTOSIS Michelle Gehringer Department of Biochemistry and Microbiology, University of Port Elizabeth, South Africa Keywords: Cell cycle, checkpoints, growth factors, mitosis, meiosis, cyclin, cyclin dependent protein kinases, G1 phase, S phase, spindle, prophase, anaphase, metaphase,
Summary: At the end of meiosis, 4 daughter cells are formed = eggs or sperm. Each contains half as many chromosomes as the parent cell (n); each cell is genetically different from its parents and from its siblings. Fertilization of an egg by a sperm restores the chromosome number to 2n.
(See figure below, where meiosis I begins with a diploid (2n = 4) cell and ends with two haploid (n = 2) cells.) In humans (2n = 46), who have 23 pairs of chromosomes, the number of chromosomes is reduced by half at the end of meiosis I (n = 23). Prophase I.