Vol. 12, Issue 11, 1673-1678, November 2002

LETTER
Segmental Polymorphisms in the Proterminal Regions of a Subset of Human Chromosomes

¹ Centre d'Etude du Polymorphisme Humain-U. INSERM 434, 75010 Paris, France; ² Institut de Génétique et Microbiologie, Université Paris-Sud, 91405 Orsay cedex, France; ³ Centre d'Etudes du Bouchet, 91710 Vert le Petit, France

The subtelomeric domains of chromosomes are probably the most rapidly evolving structures of the human genome. The highly variable distribution of large duplicated subtelomeric segments has indicated that frequent exchanges between nonhomologous chromosomes may have been taking place during recent genome evolution. We have studied the extent and variability of such duplications using in situ hybridization techniques and a set of well-defined subtelomeric cosmid probes that identify discrete regions within the subtelomeric domain. In addition to reciprocal translocation and illegitimate recombination events that could explain the observed mosaic pattern of subtelomeric regions, it is likely that homology-based recombination mechanisms have also contributed to the spread of distal subtelomeric sequences among particular groups of nonhomologous chromosome arms. The frequency and distribution of large-scale subtelomeric polymorphisms may have direct implications for the design of chromosome-specific probes that are aimed at the identification of cryptic subtelomeric deletions. Furthermore, our results indicate that the relevance of some of the telomere closures proposed within the present Human Genome Sequence draft are restricted to specific allelic variants of unknown frequencies.

[The sequence of cosmid ICRF10 (carrying DNF92) was deposited in GenBank under accession no. Y13543.]