Tables for determining the statistical significance of mutation frequencies.

Some Statistical Methods Connected with Series of Events

New data have clearly confirmed the earlier finding that specific locus mutation rates obtained with chronic gamma irradiation of spermatogonia are lower than those obtained with acute x-rays. Since this result is in contrast to classical findings for Drosophila spermatozoa, and apparently contradicts one of the basic tenets of radiation genetics, it was important to determine what factors were responsible for it. Experiments undertaken for this purpose reveal the following: (i) the lower mutation frequency is due mainly to difference in dose rate of radiation, rather than quality; (ii) a dose-rate effect is not obtained in experiments with mouse spermatozoa, confirming classical findings for spermatozoa, and indicating that the explanation for intensity dependence in spermatogonia resides in some characteristic of gametogenic stage; and (iii) a dose-rate effect is found not only in spermatogonia but also in oocytes, where cell selection is improbable, indicating that the radiation intensity effect is on the mutation process itself. A threshold response for all mutations in spermatogonia and oocytes is not a necessary consequence of the findings. Plausible hypotheses consistent with the present results can lead to other predictions. From a practical point of view, the results indicate that the genetic hazards, at least under some radiation conditions, may not be as great as those estimated from the mutation rates obtained with acute irradiation. However, it should not be forgotten that even the lower mutation rates obtained with the present intensity levels are still appreciable (16).

https://science.sciencemag.org/content/sci/128/3338/1546.full.pdf

Radiation dose rate and mutation frequency.

In this paper we compare the properties of four different general approaches for testing the ratio of two Poisson rates. Asymptotically normal tests, tests based on approximate p -values, exact conditional tests, and a likelihood ratio test are considered. The properties and power performance of these tests are studied by a Monte Carlo simulation experiment. Sample size calculation formulae are given for each of the test procedures and their validities are studied. Some recommendations favoring the likelihood ratio and certain asymptotic tests are based on these simulation results. Finally, all of the test procedures are illustrated with two real life medical examples.

Testing the Ratio of Two Poisson Rates

X-irradiation induces forward mutations from 8-azaguanine sensitvity to resistance in Chinese hamster cells in culture At this locus the number of induced mutations increases non-linearly with X-ray exposure The mutation rate increase from 42·10−7 per locus per R with 200 R to 18·10−6 per locus per R with 1200 R Several factors including cell density markedly influence the mutational yield Reversion tests using specific chemical mutagens on 72 randomly isolated, azaguanine-resistant mutants suggest that both point mutations and chromosome deletions might have occurred in the hamster cells after exposure to ionizing radiation

Mammalian cell genetics III. Characterization of x-ray-induced forward mutations in chinese hamster cell cultures

(1954). Statistical Methods for Poisson Processes and Exponential Populations. Journal of the American Statistical Association: Vol. 49, No. 266, pp. 254-266.

Statistical Methods for Poisson Processes and Exponential Populations

Some procedures for comparing Poisson processes or populations

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Statistical Methods for Poisson Processes and Exponential Populations

Some procedures for comparing Poisson processes or populations