Gene imprinting is an epigenetic phenomenon whereby alleles are expressed differently in offspring depending on whether they are transmitted from the female or male gamete. Such imprinted genes have been identified in flowering plants and mammals, and the elucidation of imprinting mechanisms has been foundational for delineating epigenetic mechanisms of gene regulation. However, the root of these discoveries dates back to 1970, when a series of experiments performed in maize unveiled the first instance of gene imprinting.

In 1970, a paper published in Genetics by Jerry Kermicle detailed his experiments to understand the basis of kernel colour phenotypes conditioned by the maize R gene. The R gene causes accumulation of the red pigment anthocyanin in aleurone, the outer visible layer of endosperm in a corn kernel. RR kernels are red, whereas rr kernels are colourless. Since 1918, it was known that crosses between an RR female parent and an rr male parent yielded solidly coloured kernels whereas crosses between an rr female and an RR male yielded mottled kernels. The endosperm of flowering plants is triploid, with a 2:1 ratio of maternal to paternal genomes. Therefore, in the first cross the endosperm genotype is RR/r, and in the second cross it is rr/R (maternal alleles/paternal alleles). Thus, a simple explanation for the observed aleurone colour phenotype is that increased dosage of the R gene (2 doses versus 1 dose) causes more anthocyanin accumulation.