It takes two to make a baby, or maybe three or four if you're
worried about passing on select genetic diseases. Doctors in the
United Kingdom announced Tuesday that they had successfully
genetically engineered embryos from parents who would have
passed on mitochondrial DNA mutations by conceiving the old-
fashioned way. The researchers reported the feat in the journal
Nature. "Because of the lack of a viable treatment for these
patients, and their families, preventing the transmission of
mtDNA [mitochondrial DNA] disease is a priority," Douglas
Turnbull, of the New Castle Institute for Brain Aging and
Vitality and colleagues wrote in the article. Mitochondria can
be found in the cytoplasm of the cells, where they produce most
of the cells energy. They have their own DNA distinct from the
50-50 mother-father split in the nucleus of a cell. A child
directly inherits only its mother's mitochondrial DNA, and in
some cases will be certain to inherit a debilitating
mitochondrial mutation. Turnbull and his colleagues