IN-VITRO RECONSTRUCTION OF THE ASPERGILLUS (= EMERICELLA) NIDULANS GENOME

A physical map of the 31-megabase Aspergillus nidulans genome is repor ted, in which 94% of 5,134 cosmids are assigned to 49 contiguous segme nts. The physical map is the result of a two-way ordering process, in which clones and probes were ordered simultaneously on a binary DNA/DN A hybridization matrix. Compression by elimination of redundant clones resulted in a minimal map, which is a chromosome walk. Repetitive DNA is nonrandomly dispersed in the A. nidulans genome, reminiscent of he terochromatic banding patterns of higher eukaryotes. We hypothesize ge ne clusters may arise by horizontal transfer and spread by transpositi on to explain the nonrandom pattern of repeats along chromosomes.