DISTRIBUTION ANALYSIS OF 7 MICROSATELLITE MOTIFS IN COSMIDS OF HUMAN-CHROMOSOME-13 LIBRARY

Cosmid library of human chromosome 13 (12,000 clones or 3.7 equivalent s of chromosome 13) was screened for microsatellite sequences (GACA)(4 ), (GACT)(4), (GATG)(4), (CAC)(5), (TCG)(5), (TCC)(5), and (GA)(n). Mo re than a thousand positive clones have been revealed. The cosmids exh ibited a nonrandom distribution of microsatellites: the clones carryin g several microsatellite sites were in excess. Five microsatellite mot ifs (GACA, GACT, TCC, CAC, and GA) clustered most frequently. Southern blotting also demonstrated clustering of microsatellite sites of the same motif. Panel hybridization of clones with ribosomal DNA probes yi elded 2% rDNA-positive cosmids. Hence chromosome 13 contains 60 repeat units of rDNA with the total length of 2.6 Mbp, which include a hundr ed each of GACA, GACT, TCC, CAC, and GA but just one GATG. The GATG si tes are the most convenient genetic markers of human chromosome 13 amo ng those tested.