Rivera H, Sitch F L, Crolla J A
Wessex Regional Genetics Laboratory, Salisbury District Hospital, England.
Genet Couns. 1995;6(4):343-7.
Telomeric translocations are uncommon: Fluorescence in situ hybridisation with TTAGGG repeats as the probe was used to search for derivative chromosomes with telomeric repeats at the break-point junction in a sample of 16 translocations with at least one terminal breakpoint and ascertained through an aneuploid patient. There were 11 cases (8 autosomal and 3 X;Y translocations) with a de novo/unknown origin in the study group and 5 control familial rearrangements. At least 20 metaphases showing a clear telomeric signal on the relevant chromosomes(s) were analysed in each individual. All 16 translocations appeared to be reciprocal events as interstitial telomeric sequences were not found. The lack of telomeric translocations in this sample may be related, among other factors, to the relative absence of tertiary monosomies which are the most suitable candidates. These data and previously published information indicate that telomeric translocations are uncommon and differ from reciprocal exchanges in several relevant ways such as an exclusive unbalanced occurrence; a consistent de novo origin and therefore a non-significant recurrence risk; restricted malsegregations, namely 3:1 tertiary monosomy and adjacent-1; a yield of "pure" imbalances, and a proneness to exhibit a jumping behaviour.
