““The real key to human gene mapping, Botstein had realized, was not finding the gene, but finding the humans. If a large-enough family bearing a genetic trait-any trait-could be found, and if that trait could be correlated with any of the variant markers spread across the genome, then gene mapping would become a trivial task. If all the members of a family affected by cystic fibrosis inevitably "co-inherited" some variant DNA marker, call it Variant-X, located on the tip of chromosome seven, then the cystic fibrosis gene had to sit in proximity to this location.””
