Efforts to resequence genetic variants that have been associated with disease may produce more questions than answers, at least at first.
Case in point: the results of Michael Stratton and Andrew Futreal of the Wellcome Trust Sanger Institute in Cambridge, UK, and their team, who have performed the largest resequencing study of its kind so far. They catalogued the protein-coding regions of 718 genes on the X chromosomes of individuals from 208 families affected by X-linked mental retardation.
By identifying variants predicted to truncate protein-coding genes and render them non-functional, the effort unearthed nine new genes probably involved in X-linked mental retardation. But it also found many similar truncating variants in normal individuals. The team estimates that people can function normally despite mutations that render 1–2% of genes on the X chromosome non-functional — a fact that could further complicate resequencing studies.