With the advances in whole genome sequencing technologies, causative mutations will be present in the data and the proportion of variation that can be captured by the sequence data is expected to approach h2. In principle, known rare risk variants, if identified, can be included in the predictor in the same way as common variants; cumulatively their contribution may be important. Their importance can be assessed by the proportion of variation they explain. Both the ability to detect an association between a trait and a SNP, and the value of including the SNP in a predictor, depend on the proportion of variance the SNP explains. For example, a rare variant with a frequency of 1/1000 in the population and a relative risk for a disease of 5 will increase the risk of disease by 5-fold for 1 in 1000 people (so from 1% to 5% for a disease with a prevalence of 1%), but such an increase in risk can also be achieved by the cumulative effect of multiple common variants with smaller effect size. The contribution of rare variants
