• Cytogenetic analysis of the action of carcinogens and tumour inhibitors indrosophila melanogaster - II. The mechanism of induction op dominant lethals by 2:4:6-tri(ethyleneimino) -1:3:5-triazine

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    • Abstract

       

      Dominant lethals induced by 2:4:6-tri(etkyleneimino)-1:3:5-triazine are due to noneucentric chromosome configurations that result in anomalous cleavage and the eventual arrest of embryonic development. The variation in the frequency of these lethals with the dose of the compound (in molar concentration) follows the same pattern as for X-rays. The curve governing this relationship when plotted semi-logarithmically approximates linearity at low doses but proceeds with a sharper gradient as the dose increases. The yield of dominant lethals by the chemical mutagen is consistently higher than mutagenically equivalent doses of X-rays, assessed on the basis of sex-linked recessive lethals.

      The quantitative theory of dominant lethals (Haldane & Lea, 1947) deduced on the basis of sister union of single-chromosome breaks and asymmetric rearrangements among two or more, was found to explain the dose/effect relationship for the chemical mutagen. The experimental dose curve was successfully fitted, and it was possible to evaluate the constants describing the properties of the induced chromosome breaks.

      The yield of dominant lethals under the effect of the inline studied varies with the stage of spermatogenesis at the time of treatment. The sensitivity pattern for the various cell stages was deduced, whence it was found that the sperm was the most susceptible This constitutes a difference from X-rays, where the most sensitive stage is an earlier germ mother cell.

    • Author Affiliations

       

      O. G. Fahmy1 Myrtle J. Fahmy1

      1. Chester Beatty Institute of Cancer Research, Royal Cancer Hospital, London, S.W.3
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  • Journal of Genetics | News

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