. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESISTANCE OF SCIARA TO EFFECTS OF IRRADIATION 313 PI 9-producing 9 by treated <? FI Aa 9-producing 9 by AA d* F Aa 9-producing & d*-p reducing 99 by AA oV v: F, Aa 99. aa the probability that the mutation will be detected in the F4 is less than %o- The calculation, of course, does not include I, the probability of induction of the muta- tion. In the sex-linked mutant strains of 6\ coprophila, male- and female-producers are phenotypically distinguishable. If one of these mutant strains is used in the experiment diagra
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESISTANCE OF SCIARA TO EFFECTS OF IRRADIATION 313 PI 9-producing 9 by treated <? FI Aa 9-producing 9 by AA d* F Aa 9-producing & d*-p reducing 99 by AA oV v: F, Aa 99. aa the probability that the mutation will be detected in the F4 is less than %o- The calculation, of course, does not include I, the probability of induction of the muta- tion. In the sex-linked mutant strains of 6\ coprophila, male- and female-producers are phenotypically distinguishable. If one of these mutant strains is used in the experiment diagrammed above, the chance of selecting a 5-pr°ducing female and a ^-producing male of genotype Aa in the F2 is % X % = % (F2 females are A A or Aa). Then the chance of selecting a female and a male of genotype Aa in the F3 is % X % - y4, making the final probability I X % X %. Thus,, the odds against detection of an autosomal recessive in 5". coprophila are at least 15:1. In digenic species like S. reynoldsi (the females produce both sons and daughters), autosomal recessives can be detected in the Fa generation according to the following scheme: P! 9 by treated <f Fj_ Aa 9 by AA tf Fp Aa 99 and Aa oV \ / ^5 1 AA : 1 aa In this case the chance of selecting an F2 male and female of genotype Aa is H x % — y±, making the odds against detection of the mutation only 3: 1 instead of 15:1. The evidence presented so far is consistent with the view that the detected mutation rate in Sciara is considerably less than the induced rate. Even so, the induced rate appears to be less than that observed in Drosophila or Habrobracon; for, in the case of the sex chromosome of 5". coprophila, where recessives can be picked up in the F2, only five factors (four recessive and one dominant) have been found. This dearth of mutants is particularly significant in view of the fact that over a period of several years the author has tested a large number of irradiated sperm (approximately 500)
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
