The identification of disease genes via molecular DNA cloning has revolutionized human genetics and medicine. Both the candidate gene approach and positional cloning have been used successfully. The defects causing Huntington's disease, facioscapulohumeral muscular dystrophy, piebaldism, Hurler/Scheie syndrome, one form of autosomal recessive retinitis pigmentosa, and a second locus for autosomal dominant polycystic kidney disease have recently been localized to chromosome 4. In addition to the rapid progress in the cloning of the 203-megabase chromosome, the presence of more than 60 closely spaced microsatellites on this chromosome will undoubtedly lead to the localization of additional disease genes. In order to consider cloned genes as potential candidates for disorders assigned to chromosome 4, it is important to collect and order all genes with respect to their chromosomal localization. Analysis of cytogenetically visible interstitial and terminal deletions should also be helpful in defining new disease gene loci and in mapping novel genes. These data represent the status quo of the integrated molecular map for chromosome 4.
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