Experiment 6.01 Objective - To study various stages of mitosis in onion root tip cells from permanent slide.

        Experiment 6.01 

Objective - To study various stages of mitosis in onion root tip cells from permanent slide. 

Requirement - Permanent slide of mitosis onion root tip cells, record file, pencil, eraser, sharpener, ruler, laboratory guide or practical book. 

PROCEDURE

1.Place the permanent slide under the microscope.

2.Observe first under the low power microscope to locate the dividing cells.

3.Then observe under the high power of microscope to examine different stages of mitosis.

OBSERVATIONS

Under low power of the microscope, rectangular cells with pink nucleus are seen scattered. Under high power of the microscope following stages become distinct 

1. Interphase

(i) It is a non-dividing phase of the cell cycle between two successive cell divisions.

(ii) Chromatin fibres appear in the form of a network within the nucleus.

(iii) Nuclear envelope and nucleolus are distinct.

Prophase

(i) Chromatin material shortens and condenses into thread like structures called chromosomes.

(ii) Each chromosome consists of two chromatids, jointed at a point called centromere.

(iii) Nuclear membrane and nucleolus start disintegration and disappear at the end of prophase.

3. Metaphase

(i) A bipolar, spindle develops in the cell. Chromosomes become thick and two chromatids of each chromosome become clear.

(ii) Chromosomes become arranged at the equator of the spindle.

(iii) Each chromosome get attached to the spindle fibres at its centromere.

Anaphase

(i) The two sister chromatids of each chromosome separate from the centromere and move towards the opposite poles.

(ii) The daughter chromosomes (separated chromatids) appear V, J, L and I shape depending upon the position of centromere.

5. Telophase

(i) The spindle disappears and the daughter chromosomes uncoil to form chromatin fibres at the two poles.

(ii) Nuclear membrane and nucleolus reappears and two daughter nuclei appear at opposite poles.

(iii) Cytokinesis occurs by cell plate formation between the two daughter nuclei.

Precaution - 1.Use fine adjustment knob of the microscope while focussing the slide under high power. 

2. Objective lens should not touch the slide.