Question

draw how does mitosis work

start with a cell containg 2 unreplicated chromosomes

Answer 1

In mitosis, the cell splits to form two identical cells that have the same DNA and same number of chromosomes as the previous cell. During mitosis one cell divides once to form two identical cells.The major purpose of mitosis is for growth and to replace worn out cells.

A cell containing 2 unreplicated chromosomes undergoes mitosis in the following five phases:

1. Interphase:

• The DNA in the cell is copied in preparation for cell division, this results in two identical full sets of chromosomes.
• Outside of the nucleus are two centrosomes, each containing a pair of centrioles that are critical for the process of cell division.
• During interphase, microtubules extend from these centrosomes.

2. Prophase:

• The chromosomes condense into X-shaped structures.
• Each chromosome is composed of two sister chromatids, containing identical genetic information.
• The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on.
• At the end of prophase the membrane around the nucleus in the cell dissolves away releasing the chromosomes.
• The mitotic spindle, consisting of the microtubules and other proteins, extends across the cell between the centrioles as they move to opposite poles of the cell.

3. Metaphase:

• The chromosomes line up neatly end-to-end along the centre (equator) of the cell.
• The centrioles are now at opposite poles of the cell with the mitotic spindle fibres extending from them.
• The mitotic spindle fibres attach to each of the sister chromatids.

4. Anaphase:

• The sister chromatids are then pulled apart by the mitotic spindle which pulls one chromatid to one pole and the other chromatid to the opposite pole.

5. Telophase:

• At each pole of the cell a full set of chromosomes gather together.
• A membrane forms around each set of chromosomes to create two new nuclei.
• The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.

Please refer the image below for better understanding.

Illustration showing the five stages of mitosis.
Image credit: Genome Research Limited