The sun is so hot that
it gives off enormous quantities of ultraviolet (UV) photons.
These can damage the DNA in your cells and cause skin cancer. The
cells of all organisms have ways of repairing most of the DNA
damage caused by UV photons. But occasionally the cell's repair
machinery makes a mistake which results in a mutation, an error in
one of the cell's genes. Many scientists believe that mutations in
skin cells sometime cause skin cancer. While sunburn is an
immediate effect of UV damage, mutations that may lead to skin
cancer accumulate over a long period of time.
While studying the effects of UV
on mutation, scientists often use single cell organisms such as
yeast and bacteria.