Construction and characterization of genomic libraries from specific human chromosomes.

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Abstract
Highly purified fractions of human chromosomes 21 and 22 were isolated from a suspension of metaphase chromosomes stained with ethidium bromide by using a fluorescence-activated cell sorter (FACS II). Two recombinant DNA libraries, representing chromosomes 21 and 22, were constructed by complete digestion of DNA from these fractions with EcoRI and insertion into the vector .lambda.gtWES.lambda.B. Clones (20) selected at random from the chromosome 22 library hybridized to EcoRI-digested human DNA, and 5 of these clones hybridized to single bands identical in size to the phage inserts. These 5 single-copy sequences and a clone coding for an 8S RNA isolated by screening the chromosome 22 library for expressed sequences were characterized in detail. Hybridization of all 6 clones to a panel of sorted chromosomes and hybrid cell lines confirmed the assignment of the sequences to chromosome 22. The sequences were localized to regions of chromosome 22 by hybridization to translocated chromosomes sorted from a cell line having a balanced translocation t(17;22)(p13q11) and to hybrid cell lines containing the various portions of another translocation t(X;22)(q13;q112). Five clones reside on the long arm of chromosome 22 between q112 and qter, while 1 clone and an 18S RNA gene isolated from the chromosome 22 library reside between pter and q112. The construction of chromosome-specific libraries by this method has the advantage of being direct and applicable to nearly all human chromosomes and will be important in molecular analysis of human genetic diseases.