The gene encoding flavanone 3-hydroxylase is expressed normally in the pale yellow flowers of the Japanese morning glory carrying the speckled mutation which produce neither flavonol nor anthocyanin but accumulate chalcone, aurone and flavanone.

The Japanese morning glory carrying the recessive mutable speckled allele with the dominant speckled-activator bears colorless flowers with fine and round colored spots distributed over the corolla whereas the plant without the speckled-activator produces pale yellow flowers. Previous chemical analysis has indicated that a mutation in the gene for flavanone 3-hydroxylase (F3H) is a likely candidate for the speckled allele. However, the F3H mRNA without sequence alteration accumulates normally in the pale yellow flowers, indicating that the speckled allele is neither the F3H gene nor a regulatory gene acting on the F3H gene expression.