INFLUENCE OF MELANIN ON MUTATION LOAD IN DROSOPHILA POPULATIONS AFTERLONG-TERM IRRADIATION

The effect of melanin on the level of mutation load has been studied i n experimental Drosophila populations exposed to radiation for 115 gen erations. Four types of populations have been analyzed: (1) control; ( 2) treated with melanin; (3) irradiated; (4) irradiated and treated wi th melanin. Melanin was produced by auto-oxidation of 1-dioxyphenylala nine and was constantly added to food. Populations were X-irradiated t wice in each generation (at the larvae stage with 6 Gy and at the imag e stage with 9 Gy). The level of recessive mutation on the third chrom osome was analyzed by a standard genetic method of balanced lethals. T he data obtained have shown that the populations exposed to long-term irradiation have the greatest number of mutations decreasing viability . Melanin exhibited radioprotective properties-it reduced the percenta ge of lethal, semilethal and subvital mutations. Thus the possibility of effective protection of populations exposed to radiation for many g enerations by melanin has been shown for the first time.