S.3 & S.4 Biology Notes Genetic And Variation Caltec S.3

Page 1 of 30 CELL DIVISON Cell division refers to the division of the nucleus and cytoplasm of a cell to form daughter cells. There are two types of cell division:  Mitosis  Meiosis MITOSIS This is the type of cell division in which two daughter cells are formed and e ach has the same number of chromosomes as the parent cell. A chromosome is a long rod -like structure that appears at cell division in a nucleus and is thought to carry hereditary material (genes). The daughter cells formed during mitosis are the same when compared to each other and to the parent. Stage involved in mitosis There are five stages involved in mitosis:  Interphase  Prophase  Metaphase  Anaphase  Telophase NB: for simplicity the process can be abbreviated as IPMAT A. Interphase During Interphase, the following occurs;  The chromosomes are long and invisible  The cell stores enough energy in form of ATP  New cell organelles (cell parts) are formed NB. Interphase is sometimes referred to as the resting stage . Page 2 of 30 B. Prophase During prophase, the following occurs;  The centrioles begin to separate and the spindle form between them  The chromosomes become short, thick and visible  The nuclear membrane disintegrates  The nucleolus disintegrates  Each chromosome is seen to consist of two chromatids C. Metaphase During metaphase, the following occurs;  The centrioles move to opposite ends of the cell  The chromosomes replicate (form exact copies of themselves ) but remain in contact along the entire length.  Chromosomes arrange themselves on the equator of the spin dle fibres D. Anaphase During anaphase, the following occurs;  The two chromatids separate at the centromere  Each chromatid moves to an opposite pole of …