Case report: chromatid exchange and predivision of chromatids as other sources of abnormal oocytes detected by preimplantation genetic diagnosis of translocations

Abstract

Preimplantation genetic diagnosis of translocations can be performed on first polar bodies (PB) at metaphase stage using FISH with whole‐chromosome painting DNA probes. Here we report the use of this method in a couple in which the female was a carrier of a balanced translocation 46, XX, t(11;16)(q21;q22). This case was unusual in that two polar bodies showed recombination events between the homologue chromosomes of 11 and 16 pairs, resulting in M‐II oocytes with monovalent chromosomes having a normal and a derivative chromatid. For this type of case, PGD analysis on polar bodies cannot give a useful result, because, at the second meiotic division, either of these chromatids could remain in the oocyte, resulting in a normal, balanced or unbalanced embryo. PGD analysis on blastomeres can provide a solution. 11 previous cases of PGD of translocations performed by metaphase PB analysis are reviewed. Copyright © 1998 John Wiley & Sons, Ltd.

The origin and significance of additional aneuploidy events in couples undergoing preimplantation genetic diagnosis for translocations by array comparative genomic hybridization

“…The approach used the technique of fluorescence in-situ hybridization (FISH) with chromosome probes specific to regions that had been translocated. Other publications soon followed (Conn et al, 1998(Conn et al, , 1999Iwarsson et al, 2000;Munné et al, 1998;Scriven et al, 1998). Later in some centres, additional probes were added to screen for common aneuploidies, but the main focus was on the translocated chromosomes.…”

Structural Chromosome Rearrangements

“…Female translocation carriers are capable of producing the same types of unbalanced 2:2, 3:1, and 4:0 segregants that have been documented in male carriers, and like their male counterparts, they produce approximately equal numbers of alternate and adjacent segregants and relatively few 4:0 segregants. In contrast, however, the 3:1 segregants that are rarely observed in sperm are a relatively common fi nding in oöcytes [136][137][138] .…”