HIGH-RESOLUTION ORDERING OF YAC CONTIGS USING EXTENDED CHROMATIN AND CHROMOSOMES

The general usefulness of fluorescence in situ hybridization (FISH) fo r the physical mapping of the human genome is greatly enhanced by impr oved DNA resolution. Several techniques have been described for decond ensing or stretching interphase chromatin in a linear fashion, allowin g long-range FISH mapping in finer detail. Highly extended linear chro matin can be hybridized over physical distances of at least several me gabases, possibly over the whole length of a chromosome. By multi-colo r FISH, we have determined the order and overlaps of YACs from a 5q34 - 35 contig. Cosmids can be localized within larger YAC clones. Extend ed chromatin mapping can be applied as an adjunct ordering technique i n genome studies.