Many genomes: variation
Mutations
Genomes change - between generations or over a lifetime - these changes are called mutations. Mutations are happening in your cells all the time. Such changes can happen spontaneously and at random. You also inherit mutations from your parents. Environmental factors like smoking and sunlight can increase the rate of DNA mutation in your cells.
If a mutation happens in a part of the DNA that does not control activity or code for a protein, the chances are that the mutation will not even be noticed by the organism. Even mutations in the coding parts of a gene won't necessarily make a difference; for example, if the letter T is swapped for an A in the codon GCT then the protein will still be the same, since both the old and the new codon still code for the amino acid Alanine.
However, some mutations can be detected because they lead to a change in the structure or the amount of protein produced. These relatively few mutations directly affect the ability of the protein to carry out its job - often resulting in a genetic disorder - or change the way the protein does its job (e.g. changing eye colour from blue to green, or earwax texture from sticky to crumbly).
Using information from the Human Genome Project, researchers are learning more about mutations with small or indirect effects on the way our bodies work. We expect to find that a number of small mutations that switch genes on at the wrong times, or produce too much or too little protein will contribute to common diseases such as diabetes and coronary heart disease.
