A disease approach using linkage analysis: Still in geneticists’ quiver

Linkage analysis, based on Mendel’s law of independent assortment, has contributed the most to the late advance of human genetics. In this article we present a way of approaching a disease by the use of this technique. The first step is to use a set of families where the disease segregates. Large pedigrees are preferable. Then all the members of these families are analyzed using an initial set of markers to detect an area of high interest. A common approach is to re-examine the same families with markers spaced closer to the chromosome in order to narrow the relevant area. Later, taking into account the existing knowledge, the hypothesis of the candidate gene is made and we try to prove it. The final study, as well as the final result are both influenced by the kind of families that are chosen, the suitability of the markers and the criteria used for proving a candidate gene hypothesis. Mendelian diseases were the first to be studied, but the real challenge for geneticists is detecting loci influencing complex diseases and linkage analysis remains still an effective approach