A library of yeast artificaial chromosomes (YACs) was constructed from a human/hamster somatic cell hybrid containing human chromosome 21 (q11-qter). Cells were embedded in agarose, and the DNA was partially digested with EcoRI, released into solution by agarase treatment of the agarose plugs, ligated into pYAC4, and transferred into yeast. Doule screening of the yeast transformants with human and hamster genomic DNA allowed the selection of clones hybridizing only with human DNA. The library consists of 321 clones, amounting to 1.5 equivalents (61 Mb) of chromosome 21. The mean YAC size calculated from 178 clones is 190 ± 100 kb. Screening of the library with eight sequence-tagged sites gave six positives. Among 21 YACs tested by in situ hybridization, 17 mapped to chromosome 21.
ASJC Scopus subject areas