The Immediate Dependence of the Action of a Specific Gene in Drosophila Melanogaster Upon Fertilization

Publisher Website
Google Scholar
Abstract
A semidominant mutant erupt(er) which causes the eruption of non-faceted material in the central region of the eye, can be suppressed by a semidominant gene (Su-er) in a separate linkage group. The suppressor gene could be almost completely inactivated by exposing embryos ranging in age from approx. 8 min. to approx. 24 hrs. (after egg-laying) to 1000 r units of X-rays. In the early larval period (55 hrs. after hatching) the effect of irradiation was still almost maximal, but after 75 hrs. it had decreased rapidly and by 100 hrs. had almost completely disappeared. Irradiation of spermatocytes and oocytes separately in the mature males and females, or of both in the female after insemination but before fertilization, produced no inhibition of the suppressor effect. These observations and others indicated that the Su-er gene produced the inactivating substance within 8 min. after fertilization, and that this substance persisted unchanged in amount until some stage of the larval period, when it was either gradually used up or ceased to affect the morphogene-tic system after a certain stage of development. The fact that the blocking action of X-rays was not carried over to the next generation indicated that the suppressor gene had not mutated, but that its product had been inactivated. This detn. of the initiation of action of a specific gene is cited as an instance of primary gene action. It is different from the environmental effects on gene-controlled processes during sensitive periods, since they occur later in development, or from genetic mosaicism which concerns the segregation of alleles, since in the case of Su-er the same genotype is present at all stages.