I propose to use plasmids containing cloned DNA of human origin as probes to detect individual, polymorphic variation in DNA fragments produced by restriction enzyme digestion (RFLP's). Probes are pBR322 plasmids containing cDNA from human liver mRNA, specifically, mRNA for the enzyme argininosuccinate synthetase (AS), group-specific component albumin and other liver enzymes and plasma proteins. The recombinant plasmids are available from the research group of A.L. Beaudet, Baylor College of Medicine, Houston, who has provided them to me for this project. To date, using an AS clone (pAS-1), I have screened 40+ individual DNA's using 6 restriction enzymes. Findings are 1.) pAS-1 hybridizes with sequences on more than 7 human chromosomes including X and Y, 2.) there is a high frequency Hind III RFLP on chromosome 9, 3.) there is an independent BamH I RFLP (not on 9), 4.) these variants segregate in families, 5.) additional variation is observed with Msp I, 6.) pAS-1 hybridizes to DNA from non-human primates and could be used as an RFLP probe in these species as well. I intend to apply a panel of at least 16 more restriction enzymes to these DNA's with the expectation of finding considerable additional variation. A unique feature of this proposal is the opportunity to detect polymorphic variants on the human Y chromosome and to study their population distribution. Methods are growth of plasmid in E. coli K12; harvest, insert excision and 32P-labeling; preparation of DNA from human cells; restriction digestion, electrophoresis and "Southern" transfer; hybridization and autoradiography. Cells are lymphocytes from volunteer donors (including several families), cultured cells with chromosomes abnormalities, and hybrid cells containing human chromosomes on a rodent background. Additional methods are genetic typing of family members at a number of loci for linkage determination and typing population samples at loci known to be linked to specific RFLP's. Goals are to establish additional RFLP's on a number of human chromosomes, to determine the population distribution of these variants, to assign them to specific chromosome regions and linkage groups, and to use information to reconstruct recent evolutionary history. Disciplines are human population, biochemical and molecular genetics. RFLP's are a major new tool for prenatal genetic counseling and genetic diagnosis.