Isolation of human chromosome 21-specific cosmids and their uses in mapping of cosmid contigs on chromosomal subregions

Abstract

SummaryA cosmid library of 3 • 10 .5 clones has been constructed from a human • hybrid cell line, 153E9a3, which contains human chromosome 2l (HC21) as the only human chromosome. From 56,500 clones of this library, 229 HC21-specific cosmids have been isolated by their hybridization to total human DNA and by their failure to hybridize to total Chinese hamster DNA. The cosmids isolated were then characterized, of these, 28 cosmids (12.2~ of those tested) contained Notl site(s), and 41 cosmids were localized on the eight subregions of HC21 by differential hybridization with Alu-PCR products obtained from a hybrid mapping panel. The cosmids localized were further integrated into the existing contigs using the end-specific probes of the clone insert. Therefore, they provided useful anchor points for contig mapping and walking.