Linkage Analysis

We will type anonymous DNA markers spaced over the whole genome in multiplex families and look for co-segregation of each marker with the disease.

Two genes are called "linked" when they are situated close together on the chromosome so they are not separated by recombination and hence inherited together from generation to generation. A family shows linkage with a marker when all affected family members share the same marker allele whereas unaffected family members have different ones.

Each family only provides small evidence for or against linkage. It also could be that the observed co-segregation happened by chance. We therefore calculate the evidence for linkage over several families and consider only when the combined evidence reaches odds > 1000:1 as significant.

Because we know the location of the marker we conclude from this that an epilepsy susceptibility gene has to be close by.

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