THE GENETIC ANALYSIS OF A RECIPROCAL TRANSLOCATION, eT1(III; V), IN CAENORHABDITIS ELEGANS

Abstract

The Caenorhabditis elegans mutation e873, which results in a recessive uncoordinated phenotype (formerly named Unc-72) and which had been isolated after ³²P t reatment (BRENNER1 974), has now been found to act as a crossover suppressor and to be associated with a translocation between linkage groups (LG's) IIIand V. The translocation has been named, eTl(ZI1; V); eT1acts as a dominant crossover suppressor for both the right half of LGIIIand the left half of LGV,providing a balancer for a total of 39 map units. The uncoordinated e873phenotype has been shown to be a consequence of Eminactive unr- 36111gene. It was possible to demonstrate that, in translocation heterozygotes, eT1chromosomes marked with either sma-3or dpy-11segregate from normal LGIII,while those marked with bli-5, sm-2or unc-42segregate from normal LGV.Since bli-5and sma-2are normally on LGIII,and dpy-11is normally on LGV,it is concluded that: (a) eT1is a reciprocal translocation; (b) there is a breakpoint between sma-3and sma-2in LGIII(the region containing unc- 36)and one between dpy-11and unc-42in LGV;(c) thera is no dominant centromere between sma-2and bli-5on LGIII,since in eT1these genes are not linked to a LGIIIcentromere. Similarly, it is highly unlikely that there is a centromere to the left of dpy-11on LGV.The new gene order in eT1was determined by measuring recombination rates between markers in eT1homozygotes. It is concluded that the new order is: dpy-1 sma-3 (break) dpy-11 unc-60,and bli-5 sma-2 (break) unc-42 unc-51.——Thisis the first analysis of a C. eleganstranslocation with respect to reciprocity, breakpoints and new gene order.