In order to try to prevent mitochondrial DNA defects which affect 1 in 5,000 people and are usually mild, researchers in Britain hope to create human embryos that have the nuclear DNA from their parents but healthy mitochondrial DNA from an egg donor.
Times Online describes the technique: "First, an egg from a woman carrying mitochondrial defects will be fertilised in vitro using her partner's sperm. At the point of fertilisation, two "pronuclei" containing genetic material from the mother and father will be removed, and injected into an unfertilised egg from which the nucleus has been removed.
This donated egg will contain healthy mitochondria, but none of the nuclear DNA that makes up most of the human genetic code."
Doesn't that sound eerily familiar to somatic cell nuclear transfer, aka cloning. Instead of a somatic cell being taken from an adult patient, two pro-nuclei are taken from what sounds like a human zygote.
The Times Online article says it's not cloning because "the embryo that develops as a result will have a full complement of genes in its nucleus from a mother and a father. Clones created by nuclear transfer are genetically identical to the adult from which they are cloned, with the exception of their mitochondrial DNA."
I'm not buying this since cloning is cloning regardless of whether a human embryo is being cloned from a human adult or from a human embryo.