Recessive mutation in the Rec-1 gene alters the recombination pattern along the autosomes in C. elegans (Zetka and Rose, 1995). The authors concluded that the
rec-1 mutation eliminates the meiotic recombination pattern and generates a genetic map proportional to physical distance. The autosomes have pronounced gene clusters that are not detectable on the X chromosome. We have tested the effect of
rec-1 mutation on the X chromosome. Recombination frequencies between (I) Unc-1 Dpy-3 (II) Dpy-3 Unc-20 (III) Lon-2 Dpy-6 and (IV) Unc-7 Lin-15 were measured in wild type and the
rec-1 mutant background. We observed an alteration in recombination frequencies in the
rec-1 mutant background consistent with the altered pattern observed on the autosomes. The alterations were not as large as for the autosomes, and were in the direction predicted if the meiotic pattern were eliminated and the genetic distance proportional to physical distance. It has been shown that the
him-1 mutation reduces the recombination frequency at the right end of the X chromosome (Broverman and Meneely, 1994), and the total length of the chromosome is one third that of wild type. We tested
rec-1 recombination in the
him-1 background. Our data show that the
rec-1 mutation does not alter the
him-1 pattern but does change the frequency. Candidates for the gene product of
rec-1 are being analyzed. F33H2.1 gene was selected as the first candidate, however no sequence alteration was found in the
rec-1 mutant (Wicky and Rose, unpublished data). Furthermore, immunostaining of the F33H2.1 protein showed localization in the muscle dense bodies. A second candidate, F33H2.5 is currently being investigated. RNAi of F33H2.5 gave an embryonic arrest phenotype. Our search for the sequence alteration responsible for the
rec-1 mutant phenotype continues. 1) Zetka, M., and Rose, A. M., (1995). Mutant
rec-1 eliminates the meiotic pattern of crossing over in C. elegans . Genetics, 141: 1339-1349. 2) Broverman, S. A. and Meneely, P. M. (1994). Meiotic mutants that cause a polar decrease in recombination on the X chromosome of C. elegans . Genetics 136, 119-127.