The structure of duplications on human acrocentric chromosome short arms derived by the analysis of 15p

We report the molecular analysis of a 130-kb DNA region containing a juncti on between beta and non-beta satellite DNA from chromosome 15p. The genomic region is characterized by beta satellite blocks intermingled with variant s of the D4Z4 repeat, and duplicons from 4q24 and 4q35. Besides the p-arm o f acrocentric chromosomes, the duplicons showed a wide genomespread involvi ng pericentromeric, sub-telomeric, and interstitial regions. In this regard , the paralogous sequences were characterized by a high similarity index (9 6%), thus indicating a recent transposition during the evolution. The acroc entrics differedwith regard to the location of the 4q24 paralogous region, since it mapped on the p-arm of chromosomes 13-15 and 21, but only on 22q11 .2. Conversely, the 4q35 duplication marked the p-arm of all the acrocentri cs. In different individuals, the short arm of acrocentric chromosomes reve aled a great variability of sequence representation and location at p11 and /or p13 for both the 4q24 and 4q35 duplications. The studied genomic region from chromosome 15p, of which a contig of approximately 200 kb has been de rived, could lead to more detailed investigations into the sequence organiz ation and possible biological function of chromosome regions that are locat ed close to the rDNA array.