Bayesian analysis was performed to examine the single-nucleotide polymorphism (SNPs) neighborhood patterns in cattle using 15,110 SNPs, each with a flanking sequence of 500 bp. Our analysis confirmed three well-known features reported in plants and/or other animals: (1) the transition is the most abundant type of SNPs, accounting for 69.8% in cattle; (2) the transversion occurs most frequently (38.56%) in cattle when the A + T content equals two at their immediate adjacent sites; and (3) C ↔ T and A ↔ G transitions have reverse complementary neighborhood patterns and so do A ↔ C and G ↔ T transversions. Our study also revealed several novel SNP neighborhood patterns that have not been reported previously. First, cattle and humans share an overall SNP pattern, indicating a common mutation system in mammals. Second, unlike C ↔ T/A ↔ G and A ↔ C/G ↔ T, the true neighborhood patterns for A ↔ T and C ↔ G might remain mysterious because the sense and antisense sequences flanking these mutations are not actually recognizable. Third, among the reclassified four types of SNPs, the neighborhood ratio between A + T and G + C was quite different. The ratio was lowest for C ↔ G, but increased for C ↔ T/A ↔ G, further for A ↔ C/G ↔ T, and the most for A ↔ T. Fourth, when two immediate adjacent sites provide structures for CpG, it significantly increased transitions compared to the structures without the CpG. Finally, unequal occurrence between A ↔ G and C ↔ T in five paired neighboring structures indicates that the methylation-induced deamination reactions were responsible for ∼20% of total transitions. In addition, conversion can occur at both CpG sites and non-CpG sites. Our study provides new insights into understanding molecular mechanisms of mutations and genome evolution. Footnotes ↵ 2 Present address: Department of Dairy Science, University of Wisconsin, Madison, WI 53706. Communicating editor: C. H aley Received April 30, 2008. Accepted June 19, 2008. Copyright © 2008 by the Genetics Society of America
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