Figure 1
Single nucleotide frequency distribution in human genes. Note the fluctuations of nucleotide frequencies in the proximity of boundaries, such as splice sites, transcription initiation, and polyadenylation site. Such variations are probably caused by the presence of regulatory elements within those regions. Also note the GC and TA biases (skews) in all noncoding, transcribed portions of the genes. The biases reflect the mutation asymmetry on the sense and antisense strands, possibly caused by the action of transcription-coupled DNA repair.
