Figure 1.

Mutations in ver cause telomeric fusions. (A) Examples of TAs in ver mutant neuroblasts. ver mutants show two types of TAs: single TAs (STAs), in which a single telomere associates with either its sister or a nonsister telomere, and double TAs (DTAs), wherein a pair of sister telomeres joins with another pair. In wild-type cells, the frequency of putative TAs is <0.01 per cell (n = 500). (Panel a) Control (Or-R) metaphase. (Panel b) ver¹/ver¹ metaphase with a 2-3 dicentric chromosome generated by a DTA (arrow). (Panel c) ver²/ver² metaphase showing XL-2 (arrow) and 4-4 (arrowhead) dicentric chromosomes, a ring X chromosome (asterisk), and a tricentric 2-3-2 chromosome (diamond), all generated by DTAs. (Panel d) ver²/Df(3L)sex204 metaphase containing 2-2 (arrow) and 4-4 (arrowhead) dicentric chromosomes and a dicentric ring involving both X chromosomes (asterisk), all generated by DTAs. (B) Frequencies of TAs in ver mutants. The TA frequencies in ver¹/ver² and ver¹/Df(3L)sex204 mutants are significantly higher than that observed in ver¹ homozygotes (P < 0.01, with Students t-test); the TA frequencies observed in ver²/ver² and ver²/Df brains are not significantly different. At least 200 cells from at least four brains were scored for each genotype.