ALIGNMENT OF THE GENETIC AND PHYSICAL MAPS IN THE DPY-5 BLI-4 (I) REGION OF C-ELEGANS BY THE SERIAL COSMID RESCUE OF LETHAL MUTATIONS

Lethal mutations in the 0.5 map unit region between dpy-5 and bli-4 on chromosome I in Caenorhabditis elegans were serially rescued using co smid-containing transgenic strains. All the lethal mutations analyzed came from a set of 495 EMS-induced. sDpr2-rescued lethals described pr eviously. Germline transformation with cosmid DNA was used to create 2 5 transgenic strains bearing heritable extrachromosomal arrays. These arrays were used as small duplications for the fine-scale mapping of e ssential genes, via the rescue of lethal mutations. Lethal mutations i n 13 essential genes have been phenotypically rescued, allowing the al ignment of the genetic and physical maps in this region. Extrachromoso mal arrays were found to be transmitted 2- to 7-fold less frequently i n oocytes than in hermaphrodite sperm for 12 of the 16 arrays that wer e examined. Three of these strains showed a subsequent 4- to 13-fold i ncrease in array stability in oocytes. This phenomenon may be influenc ed by cosmid sequences. Early mitotic loss of the arrays was observed in all 17 transgenic strains examined, suggesting that loss of the arr ay can occur at any time during development when cell divisions are oc curring. As a result of this work, 13 of the essential loci positioned between dpy-5 and bli-4 are anchored to the physical map, thereby pro viding links between the physical and genetic maps on average every 85 kb.