In Corn, Red Kernels (PP) Are Typically Dominant to White

In corn, red kernels (PP) are typically dominant to white kernels (pp). A red plant was crossed with a white plant to produce a Pp heterozygote with red kernels. However, in one ear of corn, a partially white kernel appeared unexpectedly. This kernel was grown into an adult plant, and for several generations of crosses, the offspring of this original kernel all had a mix of partially red and partially white kernels. However, when the seeds were grown in the presence of a demethylating drug, all of the resulting plants had red kernels. Explain why the mixed-color kernel appeared, why the offspring of this kernel also had the mixed-color phenotype, and why the demethylating drug had its effect.