Germ Cells and Epigenetics

Abstract

All multicellular organisms begin life as a single cell, the zygote, created by the union of two germ cells, an oocyte and a sperm. Although scientists have understood for decades that the quantity of DNA an individual inherits from each parent is equivalent, a 1984 discovery by McGrath and Solter revealed that these genes are used differently depending on whether the genes are inherited from the mother or the father (McGrath & Solter 1984). These two scientists used the technique of nuclear transplantation — when the nucleus of one cell is removed and placed into another cell — and asked two questions: Can mouse embryos derived from the nuclei of two oocytes create a viable embryo? What about nuclei from two sperm? They found that these uniparental embryos were not viable and concluded that both maternal and paternal nuclear genomes are necessary for proper embryonic development. But why?