• W. L. Stevens

      Articles written in Journal of Genetics

    • The analysis of interference

      W. L. Stevens

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      Various methods are in use for calculating a quantity to measure the interference between recombination in non-adjacent segments. Three are investigated in this paper and are shown to be unsatisfactory, because they lead to results which depend not only on the two segments in question, but also on the location of other genes followed in the experiment. Two of them, including the most popular, have expectations less than unity in the absence of interference. Since equality to unity is taken as a criterion of non-interference, this has led to erroneous conclusions.

      The exact method, which is given in this paper, while being free from the above objections, is just as simple in calculation. A formula is derived for the standard error of this estimate.

      Coincidences have been recalculated for theX- and II-chromosomes ofDrosophila. In theX-chromosome, the coincidence rises steadily to unity for extreme segments. Between segments in different arms of the II-chromosome coincidences approximate to unity, showing absence of interference. Finally a statistical analysis of the II-chromosome data has been made to prove that there is no interference across the spindle fibre attachment.

    • Tables of the recombination fraction estimated from the product ratio

      W. L. Stevens

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    • Accuracy of mutation rates

      W. L. Stevens

      More Details Abstract Fulltext PDF

      The use of the standard error of estimates of mutation rates, and other small proportions, is shown to be highly erroneous. A table is provided for rapidly making the exact tests of significance.

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