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Comparative and Functional Genomics
Volume 2008, Article ID 879023, 6 pages
Research Article

Protein Coding Gene Nucleotide Substitution Pattern in the Apicomplexan Protozoa Cryptosporidium parvum and Cryptosporidium hominis

1Department of Computer Science, Tufts University, Medford, MA 02155, USA
2Department of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA

Received 18 November 2007; Accepted 29 March 2008

Academic Editor: Neil Hall

Copyright © 2008 Guangtao Ge et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cryptosporidium parvum and C. hominis are related protozoan pathogens which infect the intestinal epithelium of humans and other vertebrates. To explore the evolution of these parasites, and identify genes under positive selection, we performed a pairwise whole-genome comparison between all orthologous protein coding genes in C. parvum and C. hominis. Genome-wide calculation of the ratio of nonsynonymous versus synonymous nucleotide substitutions ( ) was performed to detect the impact of positive and purifying selection. Of 2465 pairs of orthologous genes, a total of 27 (1.1%) showed a high ratio of nonsynonymous substitutions, consistent with positive selection. A majority of these genes were annotated as hypothetical proteins. In addition, proteins with transmembrane and signal peptide domains are significantly more frequent in the high group.