SEQUENCING 39,350 BP OF SACCHAROMYCES-CEREVISIAE CHROMOSOME-XII UTILIZING ORDERED SHOTGUN LIBRARIES

A 39,350 bp cosmid containing DNA of Saccharomyces cerevisiae chromoso me XII was sequenced by making use of ordered sub-clones of 1 kb inser t-length selected from a physical clone map. In a first analysis, 96 c lones were sequenced from both ends (10 gels) with two standard sequen cing primers covering 91% of the total sequence (49% double-stranded). After selection of another eight clones six gaps of a total of 1.8 kb and several single-stranded stretches remained. These gaps were close d by 86 primer walks leading to an overall redundancy of 4.4 per base and a total of 292 sequencing reactions. The number of walking primers can be reduced significantly by more uniform clone lengths and longer sequencing reads, thus, the total amount of sequencing reactions can approach the minimum value achieved with primer walking strategies, wi th only very few walking primers needed for gap closure.