Diagnosis of genetic disease through linkage analysis

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Diagnosis of genetic disease through linkage analysis The identification of linkage to a marker locus is very often the first step on the way to cloning a disease gene (see the next section). However, it also immediately provides diagnostic opportunities even before the disease gene itself has been identified and often when absolutely nothing is known about the nature of the underlying genetic defect. In this pedigree (which you will recognise as being the phase known pedigree above with added children) an autosomal dominant mutation is present. The disease gene has not been identified but it is known to be closely linked
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Unformatted text preview: to DNA marker polymorphisms Aa and Bb and to map between them. Clearly, in this family the mutant disease gene is present on the chromosome which happens to have alleles A and B on it. [Remember that Aa and Bb have nothing whatsoever to do with the disease, they are simply two bits of the genome which are polymorphic and which are within about a million basepairs of the disease gene.] The unborn baby can be tested to see which alleles it has inherited from its father at the two marker loci. If it has inherited A and B then it almost certainly has also inherited the disease mutation....
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