Mitochondrial gene order adjacent to the control region in crocodile, turtle, and tuatara.

We used the polymerase chain reaction and sequencing of mitochondrial gene junctions adjacent to the 5' end of the control region (light strand orientation) and the 3' end of ND6 to assess whether a representative crocodilian, turtle, or tuatara shares a unique mitochondrial gene order that is found in birds but not in mammals or amphibians. Turtles and crocodiles have the same gene order as mammals, except that crocodile has a tRNAPhe gene inserted between tRNAPro and the 5' end of the control region. Two different arrangements were detected at the 5' end of the control region in the tuatara, one resembling the mammalian (but with tRNAThr absent) and one resembling the avian gene order. Our data are consistent with the hypothesis that some tuatara mtDNAs within a single individual have undergone a deletion that removed the genes coding for cytochrome b and tRNAPro as well as 87 bp of the control region.