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Robertsonian translocations carry reproductive risks that are dependent on the chromosomes involved and the sex of the carrier. We describe five couples that presented for preimplantation genetic diagnosis (PGD).

A couple were referred for preimplantation genetic diagnosis (PGD) following diagnosis of a reciprocal translocation in the female partner: 46,XX,t(14;22)(q11.2;q13.3). PGD was carried out using fluorescence in situ hybridization (FISH) with probes specific for the translocated and centric segments of chromosome 22. An initial cycle was unsuccessful, producing 11 embryos for biopsy, only one of which, when followed up on day 4, yielded more than 10 nuclei (median 7.5, n=10). In addition, five of the embryos showed mosaic or chaotic chromosome constitutions; some of these embryos had fragmented or multilobed abnormal nuclei, hindering interpretation of the FISH signals. The single embryo transferred did not result in a pregnancy. A second cycle, using a revised protocol, produced 10 embryos, three of which were transferred, resulting in an ongoing singleton pregnancy. All the remaining embryos yielded 12 to 23 nuclei by day 4 (median 17, n=7). Apart from some tetraploid nuclei, only one embryo showed mosaicism. The significance of the changes in protocol leading to the successful outcome is discussed, and the pattern of meiotic segregation products is analysed and compared with other previous reports of reciprocal translocations. Copyright © 2000 John Wiley & Sons, Ltd.

A couple were referred for preimplantation genetic diagnosis (PGD) following diagnosis of a reciprocal translocation in the female partner: 46,XX,t(14;22)(q11.2;q13.3). PGD was carried out using fluorescence in situhybridization (FISH) with probes specific for the translocated and centric segments of chromosome 22. An initial cycle was unsuccessful, producing 11 embryos for biopsy, only one of which, when followed up on day 4, yielded more than 10 nuclei (median 7.5, n=10). In addition, five of the embryos showed mosaic or chaotic chromosome constitutions; some of these embryos had fragmented or multilobed abnormal nuclei, hindering interpretation of the FISH signals. The single embryo transferred did not result in a pregnancy. A second cycle, using a revised protocol, produced 10 embryos, three of which were transferred, resulting in an ongoing singleton pregnancy. All the remaining embryos yielded 12 to 23 nuclei by day 4 (median 17, n=7). Apart from some tetraploid nuclei, only one embryo showed mosaicism. The significance of the changes in protocol leading to the successful outcome is discussed, and the pattern of meiotic segregation products is analysed and compared with other previous reports of reciprocal translocations. Copyright © 2000 John Wiley & Sons, Ltd.

Preimplantation genetic diagnosis (PGD) offers polymerase chain reaction tests for an increasing range of single gene defects, and fluorescence in situhybridization tests for sex determination (for X‐linked conditions) and for 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 special challenge. This paper describes the behaviour of reciprocal translocations at meiosis, discusses current methods of detecting meiotic outcomes at the preimplantation stage and outlines ways forward for preimplantation diagnosis of these common rearrangements. We also propose a more general strategy using recently developed chromosome‐specific sub‐telomeric probes, combined, if possible, with proximal probes, to form a strong diagnostic tool. Copyright © 1998 John Wiley & Sons, Ltd.

Preimplantation genetic diagnosis (PGD) offers polymerase chain reaction tests for an increasing range of single gene defects, and fluorescence in situ hybridization tests for sex determination (for X-linked conditions) and for 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 special challenge. This paper describes the behaviour of reciprocal translocations at meiosis, discusses current methods of detecting meiotic outcomes at the preimplantation stage and outlines ways forward for preimplantation diagnosis of these common rearrangements. We also propose a more general strategy using recently developed chromosome-specific sub-telomeric probes, combined, if possible, with proximal probes, to form a strong diagnostic tool. Copyright © 1998 John Wiley & Sons, Ltd.

The purpose of this communication is to revise and clarify the position regarding house mouse populations with Robertsonian chromosomes in the northern Scottish county of Caithness.Heredity (1990) 64, 25–27; doi:10.1038/hdy.1990.4

At present, women at increased risk of fetal Down syndrome because of advanced maternal age, an abnormal screening test result, or a previous affected child are offered genetic amniocentesis with full fetal karyotype analysis. The advent of reliable and efficient rapid molecular techniques for identifying numeric chromosome abnormalities raises the question of whether a full fetal karyotype analysis is necessary when samples are analyzed solely because the risk of Down syndrome is increased. Without complete karyotyping, there is a risk that chromosomal abnormalities not demonstrated by rapid trisomy testing will go undiagnosed. However, some of these fetuses would have a malformation evident on ultrasound scanning, and a complete karyotype analysis would be offered. At the same time, some abnormal genotypes will have no significant phenotypic sequelae visible by ultrasound, some may be inherited and not associated with phenotypic abnormalities, and others will be of uncertain significance, raising parental anxiety and possibly resulting in unnecessary pregnancy terminations.