Mutations happen all the time - most are absolutely harmless, some are harmful - but what are mutations?
A mutation is a change, deletion or addition of a base in a DNA code. Your DNA is a long 'string' if you like of complementary bases - these code for amino acids and in turn, these code for proteins. If one of the bases are substituted this doesn't always lead to a change in amino acid formed. This is because your DNA is degenerate. This means that more than one combination of three bases code for one amino acid.
A deletion of a base will change the amino acid coded for. This is because it causes a 'frame shift' - this moves all the bases up in the sequence - different amino acids are coded for. This in turn, affects the hydrogen bonding between the complementary base pairs. Because the hydrogen bonds are altered - this affects the tertiary structure. This means the protein produced isn't functional.
The real issues occur if mutations occur within the genes which control cell division - these are called, the "tumour suppressor genes" and the "proto-oncogenes". If mutations occur within the proto-oncogenes, then cell division is stimulated. It is uncontrolled cell division which leads to the formation of tumours and potentially cancers.
