The rate of terminal nucleotide loss from a telomere of the mosquito Anopheles gambiae

Using a single copy pUChsneo transgene insertion at the Anopheles gambiae 2 L telomere, this chromosome end was monitored by genomic Southern blots for forty-four mosquito generations. During this time, the chromosome end lost terminal nucleotides at an apparently constant rate of 55 bp/generation, w hich can be accounted for by incomplete DNA replication and does not imply exonuclease activity. No telomere elongation events were detected, suggesti ng that a previously described gene conversion event at this transgene does not occur very frequently. Moreover, no evidence for elongation by transpo sable elements was found, as described in Drosophila melanogaster. These re sults are consistent with the proposal that gene conversion between complex terminal satellite repeats that are present at natural telomeres, represen ts the major telomere elongation mechanism in A. gambiae. Such recombinatio n events between repetitive sequences would occur more frequently than betw een the single copy pUChsneo transgene on the 2L homologues.