Cytogenetic analysis of the actions of carcinogens and tumour inhibitors inDrosophila Melanogaster: III. Chromosome structural changes induced by 2:4:6-Tri(Ethyleneimino)l:3:5-Triazine

Mutagenicity of the triazine herbicides atrazine, cyanazine, and simazine in Drosophila melanogaster

Assays for dominant lethal mutations, sex-linked recessive lethal mutations, and chromosomal breakage, nondisjunction and loss were performed on Drosophila melanogaster males treated by injection or by larval feeding of the herbicides atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), cyanazine [2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine], or simazine [2-chloro-4,6-bis-(ethylamino)-1,3,5-triazine]. The three herbicides significantly increased the rate of apparent dominant lethals, but this reduction in egg hatch was probably due to physiologic toxicity to sperm. Atrazine significantly increased X-linked recessive lethals and X or Y loss after treatment by larval feeding. Injection of simazine elevated X-linked lethals, whereas treatment by larval feeding did not. None of these herbicides significantly increased partial loss of the Y chromosome nor sex chromosome nondisjunction. Much larger experiments are needed to determine with confidence the mutagenic potential of these herbicides.

CHROMOSOME BREAKAGE INDUCED IN VICIA FABA ROOT TIPS BY 2,4,6-TRI(ETHYLENEIMINO)-1,3,5-TRIAZINE

After a 12-hour treatment in 10−5 M solution of 2,4,6-tri(ethyleneimino)-1,3,5-triazine (TEM), up to 29% of Vicia and 31% of Allium root cells in anaphase had bridges or fragments. The most abundant metaphase aberrations were chromosome breaks and chromatid interchanges. Aberrations were more numerous after 6-hour treatment with 2 × 10−5 M than after 12-hour treatment with 10−5 M solution. The peak aberration frequencies were reached at 36 hours after 2 × 10−5 M treatments and slightly earlier with weaker solutions. Many chromosomes had incomplete breaks. Sister reunions of chromatids occurred with equal frequency in centric and acentric fragments. Sister reunion was 1.5 times as frequent as chromatid exchange. Along the length of the satellite chromosome, breaks occurred at random except for a slight favoring of the heterochromatic region. Per unit of length the short chromosomes were about 3 times as susceptible to breakage and exchange as satellite chromosomes. TEM introduced through cut stems had no discernible effects on Tradescantia microspore chromosomes even after 3 to 5 days of treatment.