High Gene Concentration

In addition to the distinct nature of the subtelomeric repeat region, a number of  other special features of telomere structure and biology may contribute to their potential role in chromosomal rearrangements and gene dosage imbalances.

First, the unique sequence regions of human telomeres contain the highest concentration of genes of any chromosomal region in the genome (Saccone et al., 1992). This observation was initially based on the identification of GC-rich isochores with a high frequency of CpG islands in "T-bands" at human telomeres (Saccone et al., 1992). This has subsequently been confirmed by DNA sequencing efforts for several telomeres (Flint et al., 1997a; Flint et al., 1997b; Rosenberg et al., 1997). This suggests that submicroscopic deletions or duplications at telomeres may have disproportionately greater clinical consequences than similar sized imbalances elsewhere.