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January 3, 1977

Medical News

JAMA. 1977;237(1):7-12. doi:10.1001/jama.1977.03270280009001

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The newest thing in maps —one that localizes human genes  The human gene map is beginning to look almost crowded. More than 1,200 genetic loci (locations on chromosomes where genes reside) have been identified. Most (over 1,100) are autosomal and of these, more than 120 have been assigned to specific autosomal chromosomes. As for the sex chromosomes, 96 loci have been placed on the X chromosome and 2 on the Y chromosome.Still, according to Victor A. McKusick, MD, chairman of the Department of Medicine at Johns Hopkins University School of Medicine and a geneticist of some renown, the 1,200 plus total accounts for only about a fiftieth of the total number of genes in man.The genes that have been mapped so far are called structural genes because they dictate the amino acid sequence of polypeptide chains of proteins. They also occur in single copies and assort according