Genetic reproductive risk in inversion carriers

Objective: To evaluate the risk of four inversion carriers for producing unbalanced gametes. Design: Prospective analysis of sperm nuclei by fluorescence in situ hybridization (FISH). Setting: Universitat Autonoma de Barcelona. Patient(s): Four inversion carriers. Intervention(s): A semen sample from each patient was collected and prepared for FISH. Main Outcome Measure(s): The segregation outcome of each inversion was analyzed. The presence of inter-chromosomal effects (ICE) on chromosomes 13, 18, 21, X, and Y was also evaluated. Result(s): A variable production of unbalanced gametes, which implies a heterogeneous behavior of the inversions, was detected. This variability seems to be directly related to the size of the inversion, indicating that the production of recombinant gametes in inversion carriers would not be relevant when the inverted segment,is smaller than 100 Mbp. Conclusion(s): Inversions have a well-defined reproductive effect on carriers. Carriers of inversions up to 100 Mbp have a low genetic reproductive fisk and would not usually benefit from preimplantation genetic diagnosis.