Effects of radiation over fecundity in experimental populations of Drosophila melanogaster

Abstract

In order to find out the effect of radiation on the fecundity of four experimental populations of Drosophila melanogaster, three of them were irradiated chronically at different absorved dose until reach a total of 1128.06Gy (Grays), the fourth one was the control. After a recuperation period, we extracted a total of 1461 second chromosomes of which we are going to refer; the extraction was done by means of the CyL/Pm technique, broadly use in similar experiments. The normal, deleterious and lethal genes from each population and its proportion varied among populations. Chromosomes were classified as carriers and non-carriers of lethal genes as well those originated naturally or induced by radiation, this grouping is the basis of our comparisons done using a “t” Student test. Average fecundity for each population was calculated and from them different categories of fecundity were stablished. Each chromosome assigned to a corresponding category in such a way to obtain the relative average frequency for each category. On every case, comparisons among chromosomes, carriers and non-carriers of lethal genes, differences always favoured those free of lethal. For radiation affect viability values and when compared with the control population they are different. When we split the average fecundity into categories was not possible to determine a pattern of distribution, that allowed us to indicate a radiation effect and we suggest as a possible cause of it, that the irradiated populations have not completely recovered and has prevented them to reach an equilibrium for their genetic structure after the damage originated by radiation, since most of these genes are in a dynamic process and are polygenic and its action is pleiotropic, they are in a process of being selected before reach a new equilibrium.
Key words: Drosophila, lethal genes, radiation, fecundity.