Mitosis in Onion Root Tips

Introduction to Mitosis in Onion Root Tips

The simulation “Mitosis in Onion Root Tips'” aims to investigate the different stages of mitotic cell division in onion root tip cells. A cell undergoes mitotic cell division, a process of cell duplication in which one cell divides into two genetically identical daughter cells.

Procedure

First, grow the onion roots from the onion bulb.
Take one or two roots and wash them in water on a clean, grease-free slide. Add one drop of N/10 HC1 to the root tip, followed by 2-3 drops of aceto-carmine stain, and leave it for 5–10 minutes on a burner.
Care should be taken so that the stain does not dry up.
Remove the excess stain using blotting paper, cut the part of the root that is comparatively stained more (2–3 mm), and retain it on the slide.
Discard the remaining portion.
After 10–20 seconds, put one or two drops of water on them and blot them carefully using blotting paper.
Again, put a drop of water on the root tip and mount a coverslip on it, avoiding air bubbles.
Now, slowly tap the coverslip using the blunt end of a needle so that the meristematic tissue of the root tip below the coverslip is properly squashed and spread as a thin layer of cells.
Carefully seal the margins of the coverslip using molten petroleum jelly and observe it under a microscope.

Observation

Mitosis is divided into interphase and division phases. DNA replication occurs during the interphase. The division phase again has two phases: karyokinesis and cytokinesis. The division of the nucleus is called karyokinesis. Karyokinesis is divided into prophase, metaphase, anaphase, and telophase. In the prophase, the chromosomes condense, whereas in the metaphase, the chromosomes line up on the equator of the cell. Chromatids break apart at the centromere and move to opposite poles in anaphase, followed by telophase, where two nuclei form after the nuclear membrane reforms around each group of chromosomes, and finally, cytokinesis, where the division of cytoplasm takes place by furrowing at the equator, which finally leads to the separation of daughter cells.

FAQs on Mitosis in Onion Root Tips

Q1. What is mitosis?

Ans: Mitosis is a process of cell duplication in which one cell divides into two genetically identical daughter cells. The number of chromosomes remains the same in the daughter cells as in the mother cell. It takes place in somatic cells.

Q2. Explain the different phases of mitosis.

Ans: Mitosis is divided into interphase and division phases. DNA replication occurs during the interphase, followed by the division phase. The division phase again has two phases: karyokinesis and cytokinesis. The division of the nucleus is called karyokinesis, followed by cytokinesis, where the cytoplasm divides. Karyokinesis is divided into prophase, metaphase, anaphase, and telophase.

Q3. Write a short note on metaphase.

Ans: During the metaphase of mitosis, the chromosomes are lined up in the middle of the cell, forming an equatorial plate, and each sister chromatid is attached to a spindle fibre.

Q4. Explain the process of anaphase.

Ans: Anaphase is considered the shortest stage of the cell cycle. It involves the separation of sister chromatids at the centromere and their migration to the opposite poles of the cell.

Q5. What a short note on cytokinesis.

Ans: Division of cytoplasm takes place by furrowing at the equator, which finally leads to the separation of daughter cells. In this stage, the cell divides the cytoplasm equally from the parental cell into two daughter cells.