Identification of porcine chromosomes in bivariate flow karyotypes using various methods

A. BOUVET, B. KONFORTOV, N.G.A. MILLER, J.R. MILLER & E.M. TUCKER AFRC  Institute of animal Physiology & Genetics Research, Babraham, Cambridge, UK

Porcine chromosomes were assigned to each of the 20 peaks noted in the male pig bivariate flow karyotype using a combination of indirect and direct methods. The X and Y chromosomes were localized by comparison between the male and female flow karyotypes. Total DNA content of each peak (A-T + G-C fluorescence values) in standardized tlow karyotypes vs relative length of each porcine chromosome in metaphase spreads perrnitted to assignment of porcine chromosomes 1, 2, 5, 6,10, 11, 12, 13, 14, 16,17 and 18 and confirmed the position of the Y chromosome but the positions of chromosomes 3,4,7,8,9 and 15 remained tentative. Comparison of porcine, murine and porcine + murine mix flow karyotypes with those of porcine-murine hybrids showing various porcine chromosomes in cheir mŽtaphase spreads, appeared to confirm the localisations for porcine chromosomes 5, 10, 11, 14, 16, 18 and suggested localisations for porcine chromosomes 9 and 15. In addition, no chromosomes like 1, 6, 13, 17 or Y were noted in the metaphase spreads of these hybrids and their corresponding peaks also appeared to be absent. Dot blot hybridization of 10000 flow-sorted chromosomes using a battery of probes has been started and the assignment of the Y chromosome was confirmed directly by two different porcine probes, a Y-specific repeat DNA probe and a centromeric-specific repeat DNA probe that binds to every chromosome except the Y.

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