The cells life cycle

It is vital for living cells to reproduce themselves in order to continue life, and cells undergo many divisions from the time of fertilisation to physical maturity. When a single cell undergoes division, it forms two daughter cells that are identical to the original cell. A cell may live from a few days to many years, depending on its type. Cells divide in two ways: mitosis and meiosis.

Mitosis

Mitosis is when a single cell produces two genetically identical daughter cells. It is the way in which new body cells are produced for both growth and repair. Division of the nucleus takes place in four phases (prophase, metaphase, anaphase and telophase) and is followed by the division of the cytoplasm to form the daughter cells.

Telophase

Anaphase

Fig 1.3 Stages of mitosis

Telophase

Anaphase

Prophase

• Centrioles duplicate as chromatids in the nucleus change to become individual chromosomes.

• Centrioles separate and form spindles.

Metaphase

• Chromosomes align themselves in the centre of the cell, midway between the centrioles, as the nucleus and its protective membrane disappears.

• The centromere of each chromosome then replicates.

Anaphase

• Centromeres divide and identical sets of chromosomes move to opposite poles of the cell.

Telophase

• This is the final stage of mitosis.

• Nuclear membrane forms around each nucleus and spindle fibres disappear.

• Cytoplasm compresses and divides in half.

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How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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