Example of a common SNP in dogs . Example of a common SNP in dogs. This illustration shows three short segments of DNA sequence from chromosome 37 of the dog genome. There are two sequences per dog, one from the maternal chromosome and one from the paternal. Most dogs have either a C or an A at nucleotide position 25,734,258. Each nucleotide position on a given chromosome is assigned a reference number, counting from one end of the chromosome to the other. (Note that for each chromosome, the DNA sequence of only one strand is shown; the sequence of the complementary DNA strand is not shown.)