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Heterogeneity among spermatogonia of Drosophila melanogaster in sensitivity to X-rays

Published online by Cambridge University Press:  14 April 2009

H. Slizynska
H. Slizynska
Affiliation:
Institute of Animal Genetics, Edinburgh, 9
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1. Sensitivity of Drosophila melanogaster male germ-cells to chromosome breakage by X-rays has been measured by the structural changes found in the salivary gland chromosomes of larvae from irradiated fathers and untreated mothers. The genetical effectiveness of irradiation on the same males was measured by the frequency of sex-linked lethals.

2. Assessed by the overall percentage of germ-cells carrying structural changes, sensitivity follows the well-known pattern: it is highest in spermatids and decreases over spermatozoa and spennatocytes to spermatogonia.

3. This overall sensitivity has been analysed on three levels:

(a) The proportion in successive broods of ‘positive’ males, i.e. males which respond to irradiation. The results indicate that spermatozoa and spermatids in most or all males are equally sensitive to X-rays, while in regard to spermatogonia the males represent a heterogeneous population consisting of positive and negative males. This is fully confirmed by statistical analysis which was carried out by Dr B. Woolf.

(b) The proportion of ‘sensitive’ germ-cells per positive male, i.e. germ-cells carrying at least one structural change. While the proportion of sensitive cells per positive male is about 1:3 for spermatozoa, spermatocytes and spermatogonia, it is higher for spermatids. This is the main reason for the observed increase in overall sensitivity from spermatozoa to spermatids and for its subsequent drop in spermatocytes. On the contrary, the drastic drop in overall sensitivity from spermatocytes to spermatogonia results entirely from a drop in the proportion of positive males.

(c) The distribution of breaks in sensitive cells. The clustering of breaks in sensitive cells is highest in spermatogonia, somewhat lower in spermatids, and lowest in spermatocytes and spermatozoa. It indicates that spermatogonial cells are a heterogeneous population, consisting of cells that are either highly sensitive to X-rays or not sensitive at all.

4. The fact that the sensitivity of spermatogonia varies both between and within individual males is tentatively attributed to the presence or absence of spermatogonial mitoses.

Type
Research Article
Information
Genetics Research , Volume 4 , Issue 3 , November 1963 , pp. 446 - 456
Copyright
Copyright © Cambridge University Press 1963

References

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