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Eur J Hum Genet. 2002 Dec;10(12):801-6.

Meiotic outcomes in reciprocal translocation carriers ascertained in 3-day human embryos.

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Guy's and St Thomas' Centre for Preimplantation Genetic Diagnosis, Cytogenetics Department, Guy's, King's and St Thomas' School of Medicine, London and Guy's and St Thomas' Hospital NHS Trust, London, UK.


Chromosomes involved in reciprocal translocations form quadrivalents at meiosis. These quadrivalents segregate, with or without recombination, to give 32 different meiotic outcomes, only two of which are normal or balanced. This paper presents data collected from 25 cycles of preimplantation genetic diagnosis for 18 couples carrying 15 different reciprocal translocations. Embryos were tested using fluorescence in situ hybridisation with probes for the translocated and centric segments. Overall, 47.7% (71 out of 149) of embryos tested showed signal patterns consistent with alternate segregation, 24.8% adjacent-1 segregation, 10.1% adjacent-2 segregation, 15.4% 3 : 1 segregation and 2% 4 : 0 segregation. For most translocations, alternate segregation was apparently the most frequent mode. Alternate and adjacent-1 frequencies were similar in male and female carriers; however, 5.7% of embryos from female translocation carriers showed adjacent-2 segregation and 20.0% showed 3 : 1 segregation, whilst the corresponding figures for male carriers were 20.5 and 4.5%. Overall, 2.8% of embryos were mosaic and 2.3% of embryos showed chaotic constitutions for the chromosomes tested. The pregnancy success rate for these 25 cycles was 38.8% per embryo transfer and also 38.8% per couple.

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