The "F" ears represent another type of locus interaction in a
dihybrid cross (different from that in #5). At one locus the
dominant allele (D) would normally produce a purple seed. However,
the dominant allele (I) at a second, unlinked
locus inhibits formation of purple pigment, and a yellow seed is
the result just as though the seed were homozygous recessive at the
first locus. Allele "i" does not block pigment formation, and the
recessive "d" allele produces a yellow...