Analysis of embryonic mortality frequency in Drosophila melanogaster stocks with radius incompletus mutation under inbreeding conditions

Abstract

It is known that inbreeding leads to homozygotization of alleles of the most genes. The rate of this process is determined by the degree of kinship between crossed individuals. In addition, inbred breeding is accompanied by a change in the structure and functioning of the genome of cells of females’ generative system: mutational level increases and oogenetic segregation may be violated. This leads to a decrease in the number of laid eggs and an increase in the level of embryonic mortality. This process, described as "the effect of resistance to selection," is aimed at adapting to external conditions and associated with the selection of viable offspring. The character of manifestations of mutational variability is determined to a large extent by the direction of selection. However, up to now our knowledge of the role of the genotype in controlling the level of embryonic mortality in Drosophila melanogaster stocks in conditions of inbred breeding is not deep enough. The purpose of our work was to analyze the frequency of dominant lethal mutations in Drosophila stocks from radiation-contaminated regions of Ukraine (Polesskoe and Ozero), carrying radius incompletus mutation, depending on the degree of inbreeding. It is shown that under conditions of severe inbreeding (without selection) changes in the total frequency of dominant lethal mutations have a cyclic character, which depends on the genotype of the stocks. So, in radius incompletus stock, the indicator studied increases after 10 generations of selection and remains at enough high level for 20 generations. For the stocks from radiation-contaminated territories of Ukraine with radius incompletus mutation, which are contrasting in the level of embryonic mortality, two decrease peaks are shown (for the stock ri(Oz) – after 5 and 65 generations of inbreeding) and an increase (for the line ri(Pol) – after 5 and 32 generations of inbreeding) of the total frequency of dominant lethal mutations. The main factor influencing the change in the mortality level at the stage of early embryogenesis in Drosophila carrying radius incompletus mutation is the genotype of the stocks that are used in the work. It’s contribution increases after 10 (h2gen=44.78), 15 (h2gen=45.86) and 100 (h2gen=46.36) generations of inbreeding. The effect of inbred breeding was observed after 32 (h2inbr=22.61) and 65 (h2inbr=11.89) generations. The combined effect of both factors on the total frequency of dominant lethal mutations is shown for each of the generations studied. The highest values were shown after the 5th (h2comb=53.86) and the 65th (h2comb =40.63) generations of inbred breeding.