Gamma irradiation of eggs at a very early stage of embryonic development produced facial anomalies, and at 48 to 60 hr of incubation induced deformities in the hind- and forelimbs. Strains differed in the frequency and degree of deformities in hindlimbs. Barred Plymouth Rock showed the lowest frequency, and White Leghorn the highest of the three breeds tested. The reciprocal F1 hybrids between the two breeds, when irradiated, showed that the incidence of deformities could be maternally determined. In the backcrosses, however, the paternal genotype had a strong influence on the incidence. Nagoya breed showed an intermediate incidence between the above two. Its reciprocal F1 hybrids with White Leghorn showed transgressive matrocliny, and maternal effect was apparent in the backcrosses. The heritability estimate for the frequency of hindlimb deformities was 0.303 on the average. The incidence and the magnitude of hindlimb deformities were highly correlated. The incidence was negatively correlated to the number of somites at 48 hr of incubation, but was uncorrelated with shell thickness.

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