Mitosis

Mitosis

The significance of mitosis - chromosome number

Mitosis produces two new cells which have the same number of chromosomes as the parental cell and each other. Each chromosome in the daughter cells is an exact replica of each chromosome in the parental cells. Mitosis produces cells that are genetically identical to the parent which gives genetic stability.

The significance of mitosis - growth

• Cell division increases an orgasnisms cell number so it can grow, repair tissues and replace dead cells. 
• In plant and animal embryos body cells are pdocued by mitosis, so they're genetically identical
• In adult mammals tissue such as the skin and gut lining are constnatly worn away so identical cells replace them
• Mitosis continually takes place in the bone marrow which produces red and white blood cells, also in nail beds and hair follicles
• Mitosis occurs in plants in small groups of cells, in the root and shoot apex, called meristems. These cells remain very small so for a plant to row, cell expansion must take place.

The stages of Mitosis

Prophase

This is the longest of the four stages of mitosis.

1. The chromosomes condense - they coil, getting shorter and thicker and so visible as long thin threads, eventually as pairs of chromatids.

2. Centriole pairs seperate and move to opposite poles of the cell

3. From each centriole, protein microtubules are formed making the spindle. Spindle fibres extend from pole to pole and from pole to the centromere of each chromosme.

4. Towards the end of prophase the nuclear envelope disintergrates and the nucleolus disappears.

5. During this stage, pairs of chromatids can clearly be seen lying free in the cytoplasm.

Metaphase

1. Chromosomes attach to the spindle fibres…