Schematic of how tetranucleotide frequency relates to reading frame and potential codons. (a) Tetranucleotide frequencies are calculated independently of reading frame with a 1-bp sliding window; thus, they may sample a complete codon or span two partial codons. (b) Because reverse complementary pairs are summed together, both strands are sampled. Therefore, depending on the coding strand and reading frame, there are 12 potential codons sampled by each tetranucleotide.
Dick et al. Genome Biology 2009 10:R85 doi:10.1186/gb-2009-10-8-r85