The Link Between Cancer and Mitosis
Cancer is one of the most common diseases in the developed countries,
accounting for around one in four deaths. In Britain it caused about
25% of the deaths h in 1991 and is the most common cause of death
following cardiovascular disease. There are, in fact, over 200
different forms of cancer, which is why it is not necessarily thought
of as a single disease. For example, breast cancer is the most common
form in women and lung cancer in men.
Cancers are a result of uncontrolled mitotic cell division, which is
the division of one cell to produce two genetically identical daughter
cells. The problem is cased by mutations or abnormal activation of the
genes which control cell division. We can say that a gene has been
mutated if there is a change in one of the bases; for example, one
base turns (e.g. adenine) into another base (e.g. thymine). This can
lead to uncontrolled cell division. When genes are abnormal (or have
been mutated) they are called oncogenes (onkos means tumour), about a
hundred of which have been discovered. Cancerous cells will divide
uncontrollably and repeatedly forming clones of genetically identical
cells. Therefore, thought the mutation may start off in only one cell,
it can be passed on to the cells decedents, so the daughter cells will
too have the mutated gene. Eventually an irregular mass of relatively
undifferentiated cells called a tumour is formed. By the time a tumour
is detected it may contain about a thousand, million cells, which show
abnormal changes in shape.
There are basically two different types of tumours- malignant and
benign. Tumour that spread and eventually cause ill health and death
are described as malignant. However, the majority of tumours, such as
common warts, do not spread and are described as benign.
Tumour cells can break away and spread to other parts of the body,
particularly in the bloodstream and lymphatic system, causing
secondary tumours or metastases. This process is called metastasis.
The spread of cancers in this way is probably one of the most
dangerous aspects of cancer, as it can...