Two reciprocal translocations t(9p+;13q-) and t(13q-;21q+): a study of the families.

Two reciprocal balanced translocations 46,XY,t(9;13)(p23;q21) and 46,XX,t(13;21)(q21;q21), identified by RFA-and GTG-banding, are presented along with a complete study of both families. In the second case a 3 : 1 segregation is associated with an unbalanced 2 : 2 segregation, as demonstrated in the two surviving sons: one with interchange trisomy 21 and the other with partial trisomy 13 and partial monosomy 21. This suggests that the presence of this translocation, and possibly of other translocations involving morphologically similar chromosomes, could signify a high risk of having chromosomal disorders in offspring.