Worm Breeder's Gazette 9(2): 42
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
I have been attempting to determine if transposition occurs in both the oocyte and sperm lines, and if it does to compare the relative rates of movement in these two tissues. To do this I have placed the following mutant construct, [See Figure 1], from strain CB3640 (kindly provided by Jonathan Hodgkin) in a mixed Bristol/Bergerac background. This male/female strain can be continuously propagated by crossing. The key to the analysis is that fem-1 and tra-3 are on chromosome IV and flank unc-22. By picking single spontaneous males that twitch in nicotine, mating them to unc-5 tra-3 females and scoring in the next generation whether males or females twitch, it is possible to determine in which germline the transposition event occurred. If the male progeny twitch in nicotine the unc-22 gene on the tra-3 chromosome must have been hit by Tc1 because this chromosome determines maleness. This means that the original transposition event must have occurred in the sperm line since this chromosome can only come from the father. On the other hand, if the female progeny twitch in nicotine then the unc-22 gene on the unc-5 tra- 3 chromosome must have been hit by TC1. In this case the original transposition event must have occurred in the oocyte line since this chromosome is inherited from the mother. In principal, this experiment is analogous to the Drosophila attached X mating scheme. The data: The strain constructed has a rather low activity which is useful to insure independent events but means that I have a small number of positive events. Only males which came from plates with no other twitching worms were analyzed to insure that I was monitoring the initial event. To date I have analyzed 10 events; 4 occurred in the sperm line, 4 occurred in the oocyte line and 2 are indeterminate. These latter two events are puzzling because in the test cross male and female progeny twitched in nicotine. I do not have an explanation for this observation although the time during development that transposition occurred, or recombination are two possibilities that need to be explored. I think the present data is sufficient to conclude that transposition occurs in both germlines. Taking into consideration the low numbers I would also suggest that the oocyte and sperm lines are not markedly different in their transpositional activities.