We are interested in identifying the genetic factor which is responsible for transposition and excision of Tc1 in the germ line. Ikue Mori mapped several 'mutators': loci that are responsible for germ line activation of Tc1 and that may be mobile themselves ( Genetics, 120, 397-407). We are fine mapping one of the mutators.
mut-5 (which was mapped by Ikue Mori on chromosome II between
dpy-10 and
rol-1).A three factor cross was done to map
mut-5 (in RW7474, obtained from Ikue Mori) in the interval
dpy-10 unc-4. The results were as follows: [See Figure 1] We used one of the Unc-4 Mut+ recombinants to check if in this strain the mutator was indeed linked to
unc-4 (less then 0.5 m.u. away), and results show that this is indeed the case. Since this cross indicated that
mut-5 maps closer to
dpy-10 than to
unc-4 we did a three factor cross with a
dpy-10 vab-9 strain. Among 26 selected Vab-9 recombinants 5 were found to be Mut+d 21 Mut-. This indicates that
mut-5 is to the left of but quite close to
vab-9. We distinguish two possibilities: 1.
mut-5 is a Tc1 that is transcribed in the germline as the result of its surrounding sequences (e.g. a nearby enhancer). 2.
mut-5 is a gene or another transposon, the product of which is needed for transposition of Tc1. We will screen our recombinants from the
dpy-10 ctor cross for polymorphisms that cosegregate with
mut-5. Assuming that the mutator is a mobile element itself (Tc1 or another element) we should be able to recognize it in Southern blots using as probes cosmids that map to the left of
vab-9. Once a polymorphism is identified that cosegregates with
mut-5 we will try to clone it from a Mut-5+ strain. [See Figure 2]