Abstract # 6132 Poster # 206:

Scheduled for Friday, June 19, 2015 06:00 PM-08:00 PM: (Cascade AJBCD) Poster Presentation


ANALYSIS OF HUMAN (HOMO SAPIENS) AND CHIMPANZEE (PAN TROGLODYTES) GENOMIC SEQUENCE SUPPORTS ROLE OF RDNA IN EXTREME CHROMOSOME LENGTH EVOLUTION

M. Snyder and B. Robicheau
Dept of Biology, Acadia University, Wolfville, Nova Scotia B4P 2R6, USA
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     Eukaryotic chromosomes are inexplicably long. After accounting for all known features (functional and non-functional), roughly 35% of primate genomes cannot be assigned a biological role. Ribosomal RNA genes occur as clusters of identical repeated units and undergo an unusual evolution - termed ‘concerted evolution’-that results in keeping rRNA genes identical throughout all repeated copies. We have used the genomes of human (Homo sapiens) and chimpanzee (Pan troglodytes) to test our hypothesis that rDNA genes on the edge of clusters cannot participate in concerted evolution, and thus accumulate mutations, becoming pseudogenes. The hypothesis was tested by obtaining the nearest 200 kilobases (kb) of sequence adjacent to each cluster using GenBank, and by searching for sequences derived from rDNA genes via alignments using BLAST; then comparing this result to regions of the genome far removed from rDNA clusters. The results support our hypothesis. In each nearest rDNA edge examined, an excess of rDNA-like sequence occurs compared to distant sequences (averaging 2.26 kb of 10kb proximally and 1 kb of 10 kb distally in cluster edges; compared to 0.5 kb of 10 kb from sites on chromosomes with no rDNA cluster) – inferring a trend to degradation. These results support our model of rDNA cluster mechanics and strongly suggest that at least a portion of the ‘unaccounted’ 35% of chromosomes is degenerating rDNA sequence distributed throughout the genome.