Chromosomal rearrangements involving the ends of chromosomes have emerged as an important cause of genetic disease given the gene-rich nature of the regions adjacent to the telomeres1. The importance of such subtelomeric chromosome rearrangements has been clearly shown by their observed association with unexplained mental retardation and congenital abnormalities2.

Individual subtelomere specific probes have been used to focus on particular subtelomeric regions, and have resulted in the establishment of syndromes such as the chromosome 1p36 deletion syndrome3,10and the 22q13.3 deletion syndrome4. The probes are also finding applications in the investigation of autistic disorders5, recurrent miscarriages6 and haematological malignancies7.

Cytocell’s subtelomere specific probes are located in the most distal region of chromosome specific DNA on each chromosome. Beyond this unique sequence material is the 100 to 300Kb region of telomere associated repeat followed by the cap of between 3 to 20Kb of tandemly repeated (TTAGGG)nsequence8.
The probes have been chosen from the most distal unique sequence to provide the best possible specificity, whilst also being applicable for routine use for the examination of subtelomeric enumeration and integrity.

The original second-generation set of probes is derived from PAC clones9 and was established in conjunction with the Institute of Molecular Medicine, part of Oxford University, in the UK11. Continuing product improvements have led to some substitutions with alternative cosmid (35-40Kb) or BAC (150Kb) clones to give improved signal strength or chromosome specificity. The average probe size is therefore 100Kb, and all have been mapped to within a maximum of 600Kb of the true telomere.