During the past few years in the field of chromosome biology, much attention has focused on the very tip of the chromosome - the telomere. This is because functional telomeres are essential for continuous cellular proliferation, an observation that has profound implications for our understanding of ageing and cancer. Studies of telomere biology have been aided by the discovery of numerous genes required for telomere replication in ciliates, yeast, mice and humans. But missing from this genetic pantheon has been the nematode worm Caenorhabditis elegans, one of the premier organisms for gene identification and analysis. Now, however, on page 159 of this issue, Ahmed and Hodgkin describe an elegant screen for C. elegans mutants with mortal germ lines. The first gene to be characterized from this work, mortal germline-2 (
mrt-2), plays double duty in the nucleus - it is required not only for telomere replication, but also for monitoring damaged DNA.