Scientists in Oregon have created embryos with genes from one
man and two women, using a provocative technique that could
someday be used to prevent babies from inheriting certain rare
incurable diseases. The researchers at Oregon Health & Sciences
University said they are not using the embryos to produce
children, and it is not clear when or even if this technique
will be put to use. But it has already stirred a debate over its
risks and ethics in Britain, where scientists did similar work a
few years ago. The genes they want to replace aren't the kind
most people think of, which are found in the nucleus of cells
and influence traits such as eye color and height. Rather, these
genes reside outside the nucleus in energy-producing structures
called mitochondria. These genes are passed along only by
mothers, not fathers. About 1 in every 5,000 children inherits a
disease caused by defective mitochondrial genes. The defects can
cause many rare diseases with a host of symptoms, including
strokes, epilepsy, dement