(i) Somatic cells and stem cells divide by mitosis.
(2) Mitosis is completed through two main steps,
(a) Karyokinesis 9nuclear division)
(b) Cytokinesis (cytoplasmic division)
(3) Karyokinesis is completed through 4 steps.
(a) Prophase : (i) Condensation of basically thin thread-like chromosomes starts.
(ii) Due to this, they become short and thick and they start appear along with the pairs of sister chromatids.
(iii) Centrides duplicate and each centride moves to opposite poles of the cell.
(iv) Nuclear membrane and nucleous start to disappear .
(b) Metaphase : (i) Nuclear membrane completely disappears. Chromosomes complete their condensation and become clearly visible.
(ii) All chromosomes are arranged parallel to equatorial plane (central plane) of the cell.
(iii) Special type of flexible protein fibres (spindle fibres) are formes between centrioles and centromere of each chromosome.
(c) Anaphase : (i) Centromeres split and thereby sister chromatids of each chromosome seperate and they are pulled apart in opposite directions with the help of spindle fibres. ltbr. (ii) Seperated sister chromatids are called daughter chromosomes.
(iii) In this way, each set of chromosomes reach at two opposite potes of the cell.
(d) Telephase : (i) The chromosomes which have reached at opposite poles of the cell now start to decondense due to which they again become thread like thin and invisible.
(ii) Nuclear membrane is formed arround each set of chromosomes reached at poles.
(iii) Thus two daughter nuclei are formed ina cell.
(iv) Nucleolus also appears in each daughter nucleus . Spindle fibres completely disappear.
(4) In this way , Karyokinesis completes and cytokinesis begin.
(5) Cytokinesis : The cytoplasm divides by cytokinesis and two new cells are formed which are called as daughter cells. In this process , a notch is formed at the equatorial plane of the cell which deepens gradually and thereby two new cells are formed.
(6) However, in case of plant cells, instead of the notch , a cell plate is formed exactly along the midline of the cell and thus cytokinesis is completed.
