Organization and composition of the alpha21-II region of human chromosome 21

The purpose of this project was to develop a better map of the α21-II region of human chromosome 21 in regards to size and primary sequence of the five alphoid clusters that comprise the region and to explore the evolutionary relationships that exist within and between these clusters. Several HC21 BACs were identified as containing strong sequence identities to α21-II clones and were mapped to various α21-II clusters. It was revealed that both monomeric and HOR alphoid clusters can be found in the α21-II region. Phylogenetic analysis revealed separate evolutionary histories for the monomeric and HOR sequences. The size of each of the α21-II clusters was estimated. This study finds that HC21 has a different organization of alphoid clusters compared to other characterized chromosomes. These differences are likely the result of interchromosomal exchanges between the acrocentric chromosomes.