Abstract
An experiment was designed to study the effects of various dosages of X-ray irradiation on different gene-arrangements (AR and CH) of the third chromosome ofD. pseudoobscura, with respect to quantitative characters.
Egg production showed an insignificant decline at 1500r and an increasingly strong reduction by 3000 and 4500r. Other characters studied (emergence, longevity, body size and weight) generally showed the same trend.
Irradiation of both gene-arrangements usually gave more reduction in fitness characters than did irradiation of one gene arrangement alone. Irradiation caused an increase in phenotypic variability as expressed by coefficients of variation.
Heterosis in F1 was observed for most of the characters studied, and a breakdown of heterosis in F2. Heterosis was enhanced by irradiation at higher dosages.
Relative indices of general performance indicate that the adaptive values decreased with the increase in radiation dosages. In all cases the heterozygous genotypes are the fittest while the CH/CH homozygote was the least fit.
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The present work was carried out during the author's tenure of a Fellowship (PHS Grant No. CRT-5013) given by the Roscoe B. Jackson Memorial Laboratory, Bar Harbor, Maine, U.S.A.
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Tantawy, A.O. Developmental homeostasis in X-rayed populations ofDrosophila pseudoobscura . Genetica 33, 222–243 (1963). https://doi.org/10.1007/BF01725763
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DOI: https://doi.org/10.1007/BF01725763