First 338 words of the document:
New cells are needed for an organism, or part of an organism, to
grow. They are also needed to replace cells which become worn out
and repair damaged tissue. However the new cells must have the
same genetic information in them as the originals, so they can do the
same job. Each of your cells has a nucleus containing the
instructions for making whole new cells and even an entire new you!
These instructions are carried in the form of genes. A gene is a
small packet of information which controls a characteristic, or part of
a characteristic, of your body. The genes are grouped together on
chromosomes. A chromosome may carry several hundred or even
thousands of genes. You have 46 chromosomes in the nucleus of
your cells (except your gametes sperm or ova). They come in 23
pairs. One of each pair is inherited from your father, and one from
Body cells divide to make new cells. The cell division which takes
place in the normal body cells and produces
identical daughter cells is called mitosis. As a
result of mitosis all your body cells have the
same genetic information. In asexual
reproduction, the cells of the offspring are
produced by mitosis from cells of their parent.
This is why they contain exactly the same genes
variety. How does mitosis work? Before a cell
divides it produces new copies of the
chromosomes in the nucleus. This means that
when division takes place two
genetically identical daughter cells are formed.
In some areas of the body of an animal or plant,
cell division like this carries on rapidly all of the
time. Your skin is a good example cells are
constantly being lost from the surface and new
cells are constantly being formed by cell division to replace them.