Worm Breeder's Gazette 11(4): 27a
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The physical region spanning unc-30 to dpy-4 has recently been assembled from 10 constituent cosmid contigs by the use of YACs. By considering the sizes of the YACs involved (determined from PFGs) and the pattern of cosmids to which they hybridize, it is possible to calculate that the distance covered is 2350+/-400kb. However, only 480kb of this is contained in characterized cosmids. Continuing rightwards from dpy-4, a phage which contains the tRNA(trp) gene sup- 24 identifies a 470kb YAC which does not hit any cosmids at all. This means there is approximately 3000kb of the genome for which the attendant set of cosmids amounts to less than 500kb, or 17%. These contigs were assembled in order to find the tra-3 gene, at a time when it was believed that less than 10 Mb of genomic DNA ( assuming 100Mb genome size) was not yet contained in the cosmid map. There are therefore either few such regions in the genome or this was an underestimate. Considering that many cosmid contigs were shown to overlap by a small region when YAC hybridization data juxtaposed them, and that in the general case of YAC bridged gaps estimates of the size of the gaps are small, it is more likely that there are few such regions. Nonetheless, it should be borne in mind that on the physical map, all YAC-bridged gaps are drawn arbitrarily as 5 HindIII sites long but the largest YAC-bridged gap encountered in the tra-3 region was approximately 300kb.