Primary and secondary structures of the control region in the mitochondrial genome of the sea spider Achelia bituberculata. (A) The nucleotide sequence alignment of three repeat units observed in the control region of the mitochondrial genome of A. bituberculata. The lengths of the first and second repeat units are 315 bp. The 3'-end of the third repeat is truncated by 33 bp, resulting in a shorter repeat unit (282 bp). A red box indicates a single nucleotide difference observed in the third repeat unit. Dashes indicate truncated nucleotide sequences absent from the third repeat unit. (B) Putative secondary structure predicted from a large repeat unit (315 bp). An arrow marks the position truncated in the third repeat unit. An 'A' in parentheses indicates that a 'G' appears in the first and second repeat units, but an 'A' appears in the third repeat unit in position 3057 [GenBank: AY457170].