Consensus DR2 and DR4 elements are found predominantly in AluS sequences. (A) Distribution of consensus DR2 and DR4 elements within AluJ, S and Y families in the human genome. (B) Consensus sequences of AluJ, AluY and AluS subfamilies within the region containing the DR4 and DR2 element, and frequency of consensus DR2 RARE sequences within each subfamily. The position of box B of the polymerase III promoter is provided above. The sequences of the DR4 and DR2 consensus motifs are provided below. (C) Nucleotide substitution frequencies of the CpG dinucleotide present within AGGTCAnnAGGTCG motifs in AluS sequences.