Describe the process of cell division.

a)Mitosis
-Interphase; chromosomes appear as chromatin; they duplicate to form two sister chromatids; there is synthesis of new c ell organelles and the cell builds up energy to use during cell division;
-Prophase; chromatids shorten, thicken and join at the centromere hence appear visible; homologous chromosomes pair up; centrioles move to opposite sides and spindle fibres begin to form; nuclear membrane begins to breakdown and the nucleolus begins to disappear;
-Metaphase; nuclear membrane disappears; chromosomes align themselves at the centre of cell; chromosomes are attached to the spindle fibres at the centromere;
-Anaphase; chromatids separate and move to the opposite poles due to shortening of the spindle fibres; spindle fibres begin to disappear; animal cell membrane begins to constrict;
-Telophase; chromatids collect at ends of the cells; duplicate to form chromosomes; nuclear membrane forms around each set of chromosomes; cytoplasm divides into two; chromosomes become chromatins;
b)Meiosis
-Interphase I; chromosomes appear as chromatin; they duplicate to form two sister chromatids; there is synthesis of new c ell organelles and the cell builds up energy to use during cell division;
-Prophase I; nucleolus disappears; chromosomes condense, shorten and become visible; centrioles move to the opposite ends and spindle fibres begin to form; homologous chromosomes lie side by side as bivalents/ synapsis; homologous chromosomes form chiasmata and crossing over;
-Metaphase I; homologous chromosomes arrange themselves at the centre of the cell; spindle fibres attach to the homologous chromosomes at the centromere;
-Anaphase I; homologous chromosomes separate and move to the opposite sides of the cell;
-Telophase I; the spindle fibres disappear and the cell divides into two;
-Prophase II; new spindle fibres form and chromosomes become visible;
-Metaphase II; chromosomes arrange themselves at the centre of the cell; the spindle fibres attach to the chromosomes at the centromere;
-Anaphase II; sister chromatids separate and move to the opposite sides of the cell;
-Telophase II; spindle fibres disappear; nucleolus reappears; nuclear membrane is formed around each set of chromosomes; chromatids duplicate and the cell divides;