Chromosome translocations: Segregation modes and strategies for preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) offers polymerase chain reaction te sts for an increasing range of single gene defects, and fluorescence in sit u hybridization tests for sex determination (for X-linked conditions) and f or aneuploidy detection. Patients carrying chromosome translocations with a high reproductive risk are increasingly seeking to increase their chances of a normal pregnancy with the help of PGD, for which they present a specia l challenge. This paper describes the behaviour of reciprocal translocation s at meiosis, discusses current methods of detecting meiotic outcomes at th e preimplantation stage and outlines ways forward for preimplantation diagn osis of these common rearrangements. We also propose a more general strateg y using recently developed chromosome-specific sub-telomeric probes, combin ed, if possible, with proximal probes, to form a strong diagnostic tool. Co pyright (C) 1998 John Wiley & Sons, Ltd.