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The genetic control of riboflavin in Tribolium confusum Weber, Joseph


The identity of a yellow fluorescent substance isolated from Tribolium confusum, with riboflavin was shown by the independent methods of spectrophotometry, chromatography and electrophoresis. Two decomposition products of riboflavin as well as two conjugated flavines FMN and FAD, were identified. The genetic control of riboflavin and its relationship to some mutant eye color genes in the pleiotropic hierarchy of gene effects was investigated in a series of experiments involving more than 8000 Tribolium from 11 genetically different lines. All developmental stages of individuals homozygous for a recessive pearl eye color gene, p[superscript: r] (formerly called p, but renamed) were associated with a significant, heritable reduction in riboflavin content in the body. This reduction was principally in the Malpighian tubules. In all of the other lines tested the vitamin was accumulated in the tubules in relatively high concentrations. The normal allele of this gene was found to be incompletely dominant with respect to the riboflavin phene. Changing the residual genotype of p[superscript: r] by means of two generations of recurrent selection did not detectably alter its expression. Two alleles of pearl (p and p[superscript: s]) were phenotypically identical to p[superscript: r], except at the level of the riboflavin phene. Crosses of these alleles with p[superscript: r]were shown to complement. Genetic differences in riboflavin content and the pigmentation of Malpighian tubules were shown. Individuals of the pearl phenotype (p[superscript: r], p, p[superscript: s]) always had colorless Malpighian tubules. Sexual dimorphism for riboflavin content was observed in all lines tested. The quantitative parameters of variation of the riboflavin phene were examined and its heritability was found to be high by two different comparisons.

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