757 CHROMOSOME MAPPING OF HUMAN GENES BY GENE PURIFICATION SOMATIC CELL HYBRIDIZATION AND RESTRICTION ENZYME ANLAYSIS

Abstract

A combination of techniques permits mapping of genes which can by chromosomally located by no other means. Purified genes were labelled with 32P by nick translation. Chromosomes were segregated separately in mouse/human hybrids. The purified genes were mapped on segregated chromosomes by the restriction of the DNA of the somatic hybrid cells and molecular hybridization with the radioactivity labelled genes. In the human, 300 ribosomal genes are located on five homologous chromosome pairs (13, 14, 15, 21 & 22). These genes are polymorphic and contain several populations of different genes. These experiments were designed to study whether this polymorphism is due to mutational events on a single chromosome or if they are a result of interactions between chromosomes. In these experiments a single human chromosome was analyzed by utilizing a 15/X translocation. This permitted the chromosome to be selected in a mouse HPRT-/human HPRT somatic cell hybrid. This 15/X chromosome could also be removed by selection against that chromosome using 8-azaguanidine. This technique permitted us to localize a specific variant to and only to the #15 chromosome. Evidence of the restriction analysis indicates that the polymorphism of this family of genes is a result of interchromosomal exchange.