SC frequency based on the third nucleotide is correlated differently with intron number in algal (A) and land plant (B-E) genomes. NNA, NNT, NNC and NNG are defined as the ratio of total SCs with A, T, C and G at the third position, respectively to 59 SCs. The equivalent relationships in the other genomes investigated are shown in Additional file 4: Figure S3.
Qin et al. BMC Genomics 2013 14:56 doi:10.1186/1471-2164-14-56