After a five hour journey to Vienna the sun is coming up. The dawn freshly illuminates the Romanesque-baroque cityscape of the Austrian capital as we roll into the station. In pursuit of a Viennese coffee house I amble through quiet cobbled streets. My next meeting introduces me to one of Austria’s female scientists, Denise Barlow (University of Vienna). “Epigenetics has always been all the weird and wonderful things that can’t be explained by genetics,” she quips. Denise reckons that “epigenetics is a bit like the environment of our genes”. “We know epigenetics controls genes,” she explains, “but we don’t know how much or to what extent our environment disturbs this.”

I ask her what she is working on. “You might begin by saying that new life begins from the egg and sperm your father and mother gave,” she remarks. “But there’s a trick that mammals play.” I’m all ears. “Mother and father each silence about a hundred genes.” So that means our parents don’t each contribute exactly 50% of our genes? “Instead of having two copies of every gene, for some genes you only have one copy,” she maintains. “We end up with about 200 genes that are only expressed from one of the parental chromosomes, not from both.”

“At least half of these imprinted genes are in fact growth regulators, and the genes that actually come in on the paternal chromosome in the active form are always growth promoters.” (see Mum’s the word). Denise actually identified the first mammalian gene of this kind, Igf2r, which is inherited in a silent way from dad. Mum’s active copy mops up excess growth hormone in the developing embryo. Her research team are currently elucidating the ways in which imprinted genes get switched off. In mice, the father’s Igf2r gets made from DNA into RNA, the equal and opposite RNA molecule sticks to the gene transcript preventing it from becoming a protein.