Spectra of viability mutations obtained in the X-chromosome of Drosophila melanogaster as a result of treatment of males with N-nitrosoethyl urea and gamma-rays

Spectra of mutations of viability in the X chromosome of D.melanogaster obtained by treating males with N-nitrosoethyl urea (NEU) and γ-rays (F2 analysis) are presented. In the irradiation the maximum of the curve coincis with that of the control curve and occurs in the interval of 84-104 %; in the NEU variant the maximum is shifted and occurs in the interval of 63-83 %, which reflects an increased proportion of less viable cultures in this variant. The height of a second maximum in the 0-20 % interval is 32.8 % in the NEU variant and 10.0 % in the irradiation variant; this maximum is absent is the control curve. After treatment with NEU the total number of chromosomes with hereditary alterations which more of less reduced viability, has been more than 50 %. The proportion of complete lethals in the X chromosome is 22.34 % after NEU treatment and 4.67 % after irradiation; the proportion of sublethals-% 14.96 % and 6.67 % respectively, as compared to 1.04 in the control. Among the 488 cultures treated with NEU, two cultures have been found with a very high ratio of gray males to gray females-28:10 and 26:13 respectively