A LONG-RANGE PHYSICAL MAP OF HUMAN-CHROMOSOME 21Q22.1 BAND FROM THE YAC CONTINUUM

The human Chromosome (Chr) 21q22.1 region contains several genes for c ytokines and neurotransmitters and the gene for superoxide dismutase ( mutant forms of which can cause familial amyotrophic lateral sclerosis ). A region of approximately 5.8 Mb encompassing D21S82 and the glycin amide ribonucleotide transformylase (CART) loci was covered by overlap ping YAC clones, which were contiguously ordered by clone walking with sequence-tagged site (STSs). A total of 76 markers, including 29 YAC end-specific STSs, were unambiguously ordered in this 5.8-Mb region, a nd the average interval between markers was 76 kb. Restriction maps of the YAC clones with rare-cutting enzymes were simultaneously prepared , and the restriction sites were aligned to obtain a consensus restric tion map of the proximal region of the 21q22.1 band. The restriction m ap made from 44 overlapping YACs contains 54 physically assigned STSs. By integrating the consensus map of the adjacent 1.8-Mb region, we ob tained a fine physical map spanning 6.5 Mb of human Chr 21q22.1. This map contains 24 precisely positioned end-specific STSs and 12 NotI-lin king markers. More than 39 potential CpG islands were identified in th is region and were found to be unevenly distributed. This physical map and the YACs should be useful as a reference map and as a resource fo r further structural analysis of the Giemsa-negative band (R-band) of Chr 21q22.1.