MAPPING A TELOMERE USING THE TRANSLOCATION ET1(III-V) IN CAENORHABDITIS-ELEGANS

In Caenorhabditis elegans, individuals heterozygous for a reciprocal t ranslocation produce reduced numbers of viable progeny. The proposed e xplanation is that the segregational pattern generates aneuploid proge ny. In this article, we have examined the genotype of arrested embryon ic classes. Using appropriate primers in PCR amplifications, we identi fied one class of arrested embryo, which could be readily recognized b y its distinctive spot phenotype. The corresponding aneuploid genotype was expected to he lacking the left portion of chromosome V, from the eT1 breakpoint to the left (unc-60) end. The phenotype of the homozyg otes lacking this DNA was a stage 2 embryonic arrest with a dark spot coinciding with the location in wild-type embryos of birefringent gut granules. Unlike induced events, this deletion results from meiotic se gregation patterns, eliminating complexity associated with unknown mat erial that may have been added to the end of a broken chromosome. We h ave used the arrested embryos, lacking chromosome V left sequences, to map a telomere probe. Unique sequences adjacent to the telomeric repe ats in the clone cTel3 were missing in the arrested spot embryo. The r esult was confirmed by examining aneuploid segregants from a second tr anslocation, hT1(I;V). Thus, we concluded that the telomere represente d by clone cTel3 maps to the left end of chromosome V. In this analysi s, we have shown that reciprocal translocations can be used to generat e segregational aneuploids. These aneuploids are deleted for terminal sequences at the noncrossover ends of the C. elegans autosomes.