Mutational effects on milk suckling.

The pictures on left show one-day-old pups with their stomachs filled with milk (white milk spot). A large fraction of the heterozygotes inheriting the mutant allele paternally (A) do not show milk spots as tabulated with a graph on right. On the other hand, the heterozygotes with maternal transmission of the mutant allele (B) do not show any correlation between their genotypes and phenotypes (milk spot), since the maternal allele is already silenced by genomic imprinting.