Dr. Marisa Bartolomei, a University of Pennsylvania professor of cell and developmental biology, co-director of the university's Epigenetics Institute, and winner of the 2024 March of Dimes Richard B. Johnston, Jr., MD Prize, on discovering one of the first imprinted genes, making connections between imprinted gene mutations and developmental disorders, and uncovering the exact pathways of gene imprinting defects: namely, abnormalities in DNA methylation.