Integrated Transcriptional Maps of Large DNA Regions: Towards a Transcriptional Map of Human Chromosome 21

We present here a relational mapping strategy to establish integrated physical and transcriptional maps of large DNA regions. In this study, human chromosome 21 is used as a model because a physical map spanning 40 megabases on the 21q arm has already been achieved. The first step of this global analysis is to extract most of the genic content encoded by this chromosome. For this purpose, exon-amplification and cDNA selection methods are applied in conjunction to derive expressed sequence libraries from chromosome 21-specific cosmids. These resources will constitute one of the tools necessary for the relational analysis, allowing cross-screenings between genomic and coding sequence libraries. Eventually, the new genes will represent a resource to hunt for potential candidate genes implicated in the determinism of severe diseases associated to chromosome 21.