Pregnancies from biopsied human preimplantation embryos sexed by Y-specific DNA amplification

Article Abstract:

There are over 200 identified recessive diseases linked to the X-chromosome, which affect males only. Many of these diseases can be diagnosed prenatally by the examination of fetal cells obtained by chorion villus sampling or by amniocentesis. Other diseases may not be able to be diagnosed specifically, but the sex of the fetus can be determined. If the fetus is a male, then he has a chance of having the disease, in which case abortion can be offered. With in vitro fertilization techniques, the embryos can be diagnosed for the genetic defect before implantation in the mother's uterus, and only those embryos without defects would be implanted. The first established pregnancies from embryos that were biopsied and analyzed before implantation are reported in two couples that were at risk of transmitting adrenoleukodystrophy and X-linked mental retardation. Adrenoleukodystrophy is a rare disease that is characterized by degeneration of the adrenal gland and degeneration of myelin which surrounds the cerebrum, resulting in mental deterioration and blindness. A biopsy of a single cell was taken at the stage where the embryo contained six to eight cells. Besides a reduction in cell mass, the embryos are unaffected by removal of one or two cells at the eight-cell stage. Using a technique where small amounts of DNA are amplified to levels which can be analyzed, the sexes of the embryos were determined. Only female embryos were implanted. The rates of pregnancy after transfer of biopsied embryos appears to be the same as the transfer of intact embryos. Both women were confirmed as having normal female twins as determined by chorion villus sampling and ultrasonography. The analysis of preimplantation embryos for genetic defects can diagnose other X-linked diseases such as Lesch-Nyhan and Duchenne muscular dystrophy. This technique is being developed for cystic fibrosis and for other inherited diseases where the nature of the genetic defect is known. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Abnormalities, Prevention, Fetus, Genetic aspects, Fragile X syndrome, Pregnancy, Complications of, Pregnancy complications, Fertilization in vitro, Adrenoleukodystrophy

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The first cut

Article Abstract:

A procedure called preimplantation genetic diagnosis (PGD) according to which a cell is extracted from a budding three-day-old embryo is analyzed for genetic abnormalities as an adjunct to in vitro fertilization (IVF) is described. The results might help the doctors decide which embryos are free of genetic defects and should be placed in the mother's uterus, even as they raise questions about whether removing a cell during PGD leaves a molecular mark on the embryo that somehow affects its abilities to develop.

United States, Science & research, Research, Analysis, Fertilization in vitro, Human, Human fertilization in vitro, Preimplantation diagnosis

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Genetics and the public interest

Article Abstract:

Britain's Nuffield Foundation enumerated the most important ethical questions raised by the use of genetic screening to detect familial disease. These questions include whether prior consent should be required, whether genetic information should be kept secret, whether genetic data should be used for legal reasons and whether the technique will lead to prejudice against the genetically disadvantaged such as AIDS patients. Genetic screening's benefits in diagnosing diseases justify public support for it.

Editorial, Standards, Ethical aspects, Genetic screening, Genetic testing, Bioethics

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