Several recombinants were identified and purified from a cloned library of human DNA by virtue of their homology to DNA from a mouse-human hybrid cell line containing a single human chromosome, the X, and their lack of homology to mouse DNA. Three recombinants were characterized in detail, and all were homologous to reiterated DNA from the human X chromosome. These recombinants also were homologous to reiterated sequences on one or more human autosomes and, therefore, were not X chromosome specific. The recombinant DNA fragments homologous to human reiterated X DNA were the same fragments homologous to human reiterated autosomal DNA. Digestion of genomic DNAs with several restriction enzymes revealed that the pattern of fragments homologous to one recombinant, λHb2, was the same on autosomes as on the X chromosome, suggesting that the molecular organization of these elements on the X is not distinct from their organization on autosomes.
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