Worm Breeder's Gazette 8(1): 42
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 site of the ribosomal gene cluster on embryonic metaphase chromosomes of Caenorhabditis mapped by in situ hybridization. The clone pCe7, which hybridizes to ribosomal RNA, was nick translated incorporating biotin-labeled UTP. The site of hybridization of this probe DNA was detected by a double-layer fluorescent antibody technique. In the wild type, N2 strain of C. elegans the ribosomal probe hybridized to one end of two embryonic metaphase chromosomes. In order to determine which linkage group carried the ribosomal genes, in situ hybridization was carried out with chromosomes from C. elegans strains carrying cytologically distinct translocation or duplication chromosomes. Linkage groups I, II, IV and X were tested in this way. Since the ribosomal probe was found to hybridize to an internal site, rather than to the end of mnDp10 (X;I) chromosomes, it was concluded that the ribosomal genes are located at the end of the right arm of linkage group I. The free duplication of linkage group I, sDp1 (I;f) also carries the ribosomal genes. The ribosomal genes were not deleted by a deficiency, eDf3 that includes unc54 and maps to the left of unc-54 I. Therefore the ribosomal genes are probably located to the right of unc-54. Chromosomes carrying the lethal mutation, let-209 I (Phil Anderson's balancer chromosome) displayed smaller hybridization signals than wild type, suggesting that these chromosomes carry a partial deficiency of the ribosomal gene cluster. A duplication of the ribosomal genes, eDp20 (I,II) was identified by in situ hybridization. The duplicated ribosomal genes were found to be linked to the right arm of linkage group II.