three parents has been born with the help
of a controversial new in vitro fertilization
technique. The procedure, called mitochondrial
transfer, was created to prevent
women with genetic mutations from
passing along devastating diseases to
their children. The first beneficiaries were
a Jordanian couple who had lost two
previous children and four pregnancies
to Leigh syndrome, a fatal disorder that
affects the developing nervous system. To
enable them to have a healthy baby, New
York–based fertility specialist Dr. John
Zhang took the nucleus from one of
the woman’s eggs and inserted it into a
healthy donor’s egg that had had its own
nucleus removed. The resulting egg contains
the donor’s mitochondria but genetic
information from the mother that will
determine traits like eye and hair color; it
was then fertilized with sperm from the
father. About 99.9 percent of the embryo’s
DNA came from his mother and father,
with a tiny percentage from the donor
mitochondria. The boy, now 6 months
old, is healthy, but his birth has sparked
criticism, since three-parent embryo techniques
are banned in the U.S. because of
fears they might lead to genetic abnormalities.
Zhang performed the procedure
in Mexico, and tells New Scientist he was
justified in what he did. “To save lives is
the ethical thing to do,” he said.
