Problems of Germline Therapy

Vol. 392, April 16, 1998

Sir-You recently published a full-page report of a Californian symposium on germline gene therapy, and a leading article, without a single mention of preimplantation genetic diagnosis.

If a couple are at risk of having a child with a serious genetic disease, it is now possible for them to have their embryos screened at the eight-cell stage, after in vitro fertilization, to ensure that only unaffected embryos are transferred to the uterus. Only in the very rare cases where both partners are sufferers from a recessive condition that allows survival to reproductive age, such as cystic fibrosis, will no unaffected embryos be generated. As 10-20 embryos could be produced from a single egg recovery, it would not be difficult also to avoid the birth of carriers if that was desired.

Most couples would surely prefer to avoid the transfer of affected embryos, rather than seeking to tamper with their DNA at such an early stage, with possibly unpredictable consequences. Leroy Hood, chair of molecular biotechnology at the University of Washington, said: "We are using exactly the...