The wild-type dominant allele yields brown eyes in the moth Ephestia kuehniella since it can synthesize a precursor pigment molecule, kynurenine. The a mutation interrupts synthesis of kynurenine and yields red eyes.

• In an Aa x aa cross, the aa larvae exhibit wild-type brown eyes if the Aa parent is female. These aa larvae gradually develop red eyes as they grow into adults.
  • The Aa oocyte contains sufficient kynurenine in the cytoplasm to be distributed to the cells of young larvae, who start out life with brown eyes. As the pigment is diluted among many cells as the larva grows, red eyes emerge.