Many genomes: variation
Mutations: Small changes, big differences
Small changes can make big differences in our bodies. The most common mutation to cause cystic fibrosis - a disorder where a person's internal organs become clogged with thick mucus - is the loss of 3 base pairs in the CFTR gene. A single change to the dystrophin gene sequence can cause one of the muscle-weakening conditions known as muscular dystrophy.
Swapping an A for a T in a gene for haemoglobin - the protein in our blood that carries oxygen around the body - causes a serious disease called sickle cell anaemia. In people with sickle cell anaemia, the haemoglobin includes the amino acid valine where a glutamic acid would usually be. This causes the proteins to clump together and changes the shape and behaviour of the red blood cells. However, this mutation can be beneficial: people who carry this change on only one of their chromosomes are resistant to infection by the parasite that causes malaria.
