FACT
Hair has the highest
rate of mitosis. An
average hair grows
0.3 mm every day
and 1 cm every
month.Living Process Role of Mitosis
Development and growth The number of cells increases by
mitosis enabling organisms to grow
from a single cell to a complex
multicellular organism.
Cell replacement Cells are constantly lost and replaced
by new ones in the body, for example
in the skin and in the gut. In addition,
red blood cells live for only four
months, and are replaced by mitosis.
Replacement of damaged plant or
animal tissue (regeneration)Some organisms use mitosis to replace
body parts. For example starfish
replace lost arms by mitosis.
Asexual reproduction Some organisms such as the hydra use
mitosis to produce genetically
identical offspring. The process is
known as budding. Mitosis is also the
method by which yeast cells multiply.Figure 4.3 shows asexual reproduction in a ciliate organism. Asexual reproduction uses
mitosis.
Figure 4.3: Asexual reproduction: ciliate undergoing cytokinesis.4.4 Cancer
Introduction DUMMY
Cancer is a group of diseases characterised by uncontrolled cell division which leads to
growth of abnormal tissue. This means that a cancer is essentially adisease of mitosis.
Cancer begins when a single cell istransformed, or converted from a normal cell to a cancer
cell. Cancer cells grow and divide uncontrollably to form a mass of cancer cells called a
tumour. As the tumours grow, they squash healthy cells, steal their nutrients and prevent
them from working normally. Cancer cells differ from normal cells in a number of ways:
1.Cancer cells don’t listen to signals to stop growing: normal cells listen to signals fromChapter 4. Cell division 103