title: A prenatal tertiary trisomy resulting from balanced maternal 8; 9 translocation.
abstract: An additional derivative chromosome 8 was found in the cytogenetic analyses of the chorionic villus biopsy specimen of a balanced reciprocal translocation carrier mother. This was a 3:1 segregation of the unbalanced product of the balanced maternal 8:9 translocation. The chromosomes of the carrier of the balanced reciprocal translocation pair with their matching homologous segments at meiosis I, a quadrivalent figure is formed and chromosomes segregate from this configuration. Increased nuchal tranaslucency was also determined on fetal sonography at the 13(rd) week of gestation. The final karyotype was 47,X Y,+der(8)t(8;9)(q11.2;p22) mat, and the parents were informed about this tertiary trisomy. After genetic counseling, the parents decided to terminate the pregnancy. The presented case is a reminder of the probability of the unbalanced products of the 3:1 segregation, rather than the common 2:2 segregation.
authors.affiliation: Department of Medical Genetics, Faculty of Medicine, Gazi University, Ankara, Turkey.
authors.forename: Gülsüm
authors.initials: G
authors.lastname: Kayhan
authors.affiliation: Department of Medical Genetics, Faculty of Medicine, Gazi University, Ankara, Turkey.
authors.forename: Mehmet Ali
authors.initials: MA
authors.lastname: Ergün
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Gazi University, Ankara, Turkey.
authors.forename: Aydan Asyalı
authors.initials: AA
authors.lastname: Biri
authors.affiliation: Department of Medical Genetics, Faculty of Medicine, Gazi University, Ankara, Turkey.
authors.forename: Meral Yirmibeş
authors.initials: MY
authors.lastname: Karaoğuz
keywords: 3:1 segregation; Derivative chromosome 8; nuchal translucency; reciprocal translocation; tertiary trisomy