Page 24 - Biology - XII

(iii) Nuclear membrane starts disappearing, later disappears.
(iv) Nucleous disappears.

3. Metaphase (Meta—between): This stage is identifi ed by—
(i) The chromosomes are set free as the nuclear membrane has disappeared.
(ii) The chromosomes become arranged at the centre of the equator of the cell.
(iii) The chromosomes are attached to spindle fi bres (spindle fi bres are not visible).
(iv) The chromosomes are shorter and thicker, hence, they are deeply stained.
(v) The centromere of each chromosome is on the equator of the cell (spindle fi bres attach to
centromere).

4. Anaphase (Ana—back): This stage is identifi ed by—
(i) The centromeres of chromosomes split and two sister chromatids are separated.
(ii) The two daughter chromosomes are pulled or pushed apart.
(iii) The daughter chromosomes are at opposite poles. They appear in shapes of J, V, U.

(iv) Their arms are towards the equator.
5. Telophase (Tela-end): This stage is identifi ed by—
(i) The chromosomes lose their characteristic shape.
(ii) The chromosomes become a jumbled mass-like network as it was during non-dividing stage.
(iii) Around the chromatin material, a nuclear membrane starts appearing.
(iv) Two daughter nuclei are thus formed.

(v) Spindle fi bres disappear.
(vi) Nucleoli reappear in each daughter cell.
(vii) A cell plate is formed in the centre of cells and forms two daughter plant cells.

Precautions
1. Place the slides under the objective lens and focus it fi rst under the low power (10X).
2. Focus the microscope lens on the ‘marked’ area.
3. Gently shift the lens to use high power objective (45X).

2-Daughter
1 2nd Parent cell Diploid cells
1
1st Cell division Interphase

1st Parent cell (2n) 2
2 2-Daughter
2nd cell division Diploid cells
2-Daughter cells (2n) (2n)
(2n)
Fig. 5.3: Scheme of mitotic (cell) division

23