Last week the Catholic moral theologian Jack Mahoney backed the decision of MPs to permit a procedure that will allow babies to be created using DNA from three people in order to screen out genetic diseases. The Church, and many others, oppose the move Fr Jack Mahoney is to be thanked for focusing on the key question in the debate over mitochondrial donation which is, where is the harm in it? His answer (“Where’s the harm?” The Tablet, 7 February 2015) is that there is no harm, at least if the procedure is limited to genetically modifying eggs rather than embryos. I disagree profoundly, but I agree that the question demands an answer. Where is the harm? The first concern is of physical harm to the child. Scientists from other countries have warned that there is not suff