Generation and characterization of a human chromosome 9 cosmid library

Oat-maize chromosome addition lines: a new system for mapping the maize genome

Novel plants with individual maize chromosomes added to a complete oat genome have been recovered via embryo rescue from oat (Avena sativa L., 2n = 6x = 42) x maize (Zea mays L., 2n = 20) crosses. An oat-maize disomic addition line possessing 21 pairs of oat chromosomes and one maize chromosome 9 pair was used to construct a cosmid library. A multiprobe (mixture of labeled fragments used as a probe) of highly repetitive maize-specific sequences was used to selectively isolate cosmid clones containing maize genomic DNA. Hybridization of individual maize cosmid clones or their subcloned fragments to maize and oat genomic DNA revealed that most high, middle, or low copy number DNA sequences are maize-specific. Such DNA markers allow the identification of maize genomic DNA in an oat genomic background. Chimeric cosmid clones were not found; apparently, significant exchanges of genetic material had not occurred between the maize-addition chromosome and the oat genome in these novel plants or in the cloning process. About 95% of clones selected at random from a maize genomic cosmid library could be detected by the multiprobe. The ability to selectively detect maize sequences in an oat background enables us to consider oat as a host for the cloning of specific maize chromosomes or maize chromosome segments. Introgressing maize chromosome segments into the oat genome via irradiation should allow the construction of a library of overlapping fragments for each maize chromosome to be used for developing a physical map of the maize genome.

Efficient identification and regional positioning of YAC and cosmid clones to human chromosome 21 by radiation fusion hybrids

The use of integrated mapping strategies involving bacterial, yeast, and rodent cells as hosts simplifies the construction of maps, which combine long-range order, high resolution, and easy access to the cloned DNA. Radiation-fusion hybrids offer a specially powerful long-range mapping system for human chromosomes. We describe here techniques for establishing a radiation-fusion hybrid map of Chromosome (Chr) 21q and its integration with local information on YAC and cosmid positions.

Construction and characterization of a YAC library with a low frequency of chimeric clones from flow-sorted human chromosome 9

Human chromosome 9 DNA, flow-sorted from somatic cell hybrid PK-87-9, has been used to construct two complete digest YAC libraries. The combined representation of chromosome 9 in these libraries, estimated by hybridization of chromosome 9-specific sequences to YAC colony grids, is approximately 95%. The frequency of chimeric clones, analyzed by fluorescence in situ hybridization of chromosome 9 YACs to human metaphase chromosomes, was estimated to be approximately 4%. These libraries provide a resource for physical mapping and for moving from genetic markers to disease loci on chromosome 9.