What is 'missing heritability'?
By studying families and by comparing identical and non-identical twins, researchers are able to make estimates of how much of any particular trait we develop is influenced by the genes we inherit or down to the environment we grew up in.
Take, for example, height. Genetic studies tell us that it has a heritability of around 80%, but while over 40 genes have been identified that do contribute to differences in our height, taking all these together still only accounts for 5% of the differences between us. This is despite of studies looking at many thousands of people. This difference between what we would expect to find and what we have been able to identify to date is what is known as the 'missing heritability'. This is not only true for height, but is also seen in type 2 diabetes, Crohn's disease and other complex diseases.
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