"The area to which I've given the greatest attention is a new phenomenon in molecular biology called genomic imprinting, which is a situation in which a DNA sequence can have conditional behavior depending on whether it is maternally inherited—coming from an egg—or paternally inherited—coming through a sperm. The phenomenon is called imprinting because the basic idea is that there is some imprint that is put on the DNA in the mother's ovary or in the father's testes which marks that DNA as being maternal or paternal, and influences its pattern of expression—what the gene does in the next generation in both male and female offspring."