Mitosis in Onion Root Tip (Allium Cepa)

Materials

• Onion root tips
• 1N HCl
• Acetocarmine stain
• Glycerine
• Watch glass
• Slides
• cover slip

Procedure

1. Place 2–3 root tips on a watch glass.
2. Add 2 drops of 1N HCl and gently warm it.
3. Blot the HCl with blotting paper and then add 2–3 drops of acetocarmine
   stain and warm it.
4. Allow the root tips in stain for 5–10 minutes.
5. Take the stained root tips on a slide with 2–3 drops of glycerine.
6. Place the coverslip over the slide with a blotting paper and squash it with
   a thumb

Mitosis
Mitosis is also called somatic cell division or equatorial division. The process of cell division, whereby chromosomes are duplicated and distributed equally to the daughter cells, is called mitosis. It helps to maintain the constant chromosome number in all cells of the body.

Interphase
Interphase is also called the resting stage. This is a transitional phase between the successive mitotic divisions.

1. Replication of DNA takes place.
2. The volume of the nucleus increases.
3. The chromosomes are thinly coiled.

Prophase

1. Each chromosome consists of chromatids united by a centromere.
2. Spindle formation is initiated.
3. The chromosomes shorten, thicken, and become stainable.
4. The nuclear membrane and nucleolus start disappearing.

Metaphase

1. Disappearance of the nucleolus and nuclear membrane.
2. Chromosomes are at their maximum condensed state.
3. Spindle formation is complete.
4. The chromosomes align in the equatorial position of the spindle and form the equatorial plate that is at a right angle to the spindle axis.
5. The centromeres are arranged exactly at the equatorial plate and the arms are directed toward the poles.

Anaphase

1. The centromere of the chromosomes divides and the 2 chromatids of each pair separate.
2. Sister chromatids start moving toward the opposite poles due to the contraction of chromosomal fibers.
3. The daughter chromosomes assume “V” or “J” shapes.

Telophase

1. It is the reverse of prophase.
2. The chromosomes aggregate at the poles.
3. The spindle starts disappearing.
4. The new nuclear membrane starts to reappear around each set of chromosomes.
5. The nucleolus gets reorganized.

Cytokinesis
A cell plate is formed by the formation of phragnoplast from the Golgi complex. Later the primary and secondary wall layers are deposited. Finally, the cells are divided into 2 daughter cells. The cytoplasm gets divided into 2 parts.