Summary of the extent of cow tRNA gene sequence variability. Each cow tRNA gene is compared with tRNA genes from the horse, dog, mouse, rat, human, chimpanzee, chicken and fugu genomes. The unit of mismatch is in single nucleotide bases and represents a threshold of similarity. For example a mismatch threshold of 3 includes cow tRNA genes that have 3 or less base differences to tRNA genes from other genomes. Trend lines for counts for 0–3 mismatches are shown in red and for counts for 4–13 mismatches are shown in blue.