Science | Mitosis

• Mitosis: It is a type of cell division of the nucleus that takes place in somatic or body cells such those in bones or skin.
• Why Would a Cell Divide? Besides growth a cell would also divide for: Repair or Replacement Cancer. Different cells divide at different rates: Most mammalian cells = 12-24 hours Some bacterial cells = 20-30 minutes
• How long is one cell cycle? Depends on the cell- skin cells = ~24 hours, nerve cells = never after maturity, cancer cells = very short. Remember: every cell only has a certain # of divisions it can undergo, then it dies = apoptosis (programmed cell death)
• Divided into 3 phases: G1 (1st gap) = small cell is absorbing nutrients, growing & doing its job. S (synthesis) = cell is continuing to grow & duplicates its DNA. G2 (2nd gap) = cell keeps growing & doing its job.
• THERE ARE TWO STAGES TO A CELLS LIFE: Interphase (growth & replication of DNA) Mitotic Phase (division of cell into 2 daughter cells). Cell spends about 90% of the time in interphase
• DNA is all twisted up into a Chromosome. During S phase the Chromosome is copied. 2 complete identical sets of chromosomes. They are connected in the middle by a centromere. A single copied chromosome is called a Chromatid.
• The Mitotic Phase. Divided into 4 stages of Mitosis: Prophase Metaphase Anaphase Telophase (+) PLUS Cytokinesis
• Interphase. The cell is now ready to undergo cell division. The centromeres located at the cytoplasm consist of two centrioles, which are organelles that contain important materials that help with the formation of spindle fibers that separate the chromosomes during mitosis.
• Prophase: Chromatids condense becoming visible. Nuclear membrane dissolves The centrioles (an organelle that makes microtubules) appears and migrate to opposite sides. spindle fibers start to form between them
• Metaphase: Chromosomes line-up on the metaphase plate, Centromeres are attached to spindle fibers
• Anaphase: Spindle fibers contract Centromeres divide Sister chromatids are pulled away from each other towards the poles
• Telophase: The chromosomes reach the poles Nuclear membranes form around the 2 new nuclei
• Cytokinesis: The cytoplasm distributed equally between the 2 new cells In animals, a cleavage furrow forms from outside in In plants, a cell plate forms from inside out
• The product of mitosis is 2 cells The daughter cells are identical to each other & to the mother cell
• In humans, the 2 daughter cells will have 46 chromosomes (23 pairs) Each chromosome is said to have the same gene sequence
• Mitosis is a form of asexual reproduction, New individuals are produced by 1 parent & thus, are identical to their parent