Molecular hybridization under conditions of high stringency permits cloned DNA segments containing reiterated DNA sequences to be assigned to specific chromosomal locations.

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Abstract
Identifying the specific DNA sequences involved in the chromosomal abnormalities in developmental and neoplastic diseases may be essential to understanding the molecular biology of these disorders. The use of recombinant DNA techniques in conjunction with rodent-human hybrid cells makes it possible to assign chromosomal locations to specific DNA sequences. The ubiquitous presence of reiterated DNA species often complicates the application of straightforward molecular hybridization. To accelerate the mapping of cloned sequences to specific chromosomal locations, the possibility that cloned sequences containing reiterated DNA might be used without isolating unique sequences was investigated. By varying conditions of hybridization (specifically temperature) and using restricted DNA samples from human genomic DNA, Chinese hamster ovary-human chromosome 11 hybrids and non-chromosome 11 hybrids, cloned DNA sequences containing reiterated sequences was assigned to their chromosome of origin. By hybridization under the high-stringency condition of 55.degree. C, specific banding was produced with both human genomic DNA and the human-chromosome-containing hybrid from which the probe was prepared. Using a panel of chromosome 11 deletion mutants, a cloned sequence was assigned to a specific chromosomal location. This approach will accelerate gene mapping procedures and facilitate identification of DNA sequences involved in chromosomal abnormalities.