9807100 Brown, Wes Mitochondrial DNA (mtDNA) of animals is a small, extrachromosomal genome typically about 16 kilobases and containing 37 genes. MtDNA comparisons among major animal groups suggest several generalities: 1) With the exception of some cnidarian mtDNAs, and otherwise for a single protein-encoding gene (ATP8), gene content is invariant, consisting of 37 genes. 2) Gene arrangements commonly remain unchanged over long periods of evolutionary time. 3) There is little selection for particular gene arrangements. 4) The great number of potential gene rearrangements makes convergence in different lineages unlikely. 5) With few exceptions, gene arrangements seem stable within major groups, but variable between them. All of these characteristics make the comparison of mitochondrial gene arrangements a powerful means for inferring ancient phylogenetic relationships. From these comparisons we have been able to infer several higher level evolutionary relationships for which all other types of data had been equivocal. We intend to determine the complete mitochondrial DNA sequences and gene arrangements of an animal representing each of the following groups: The crustacean groups Remipedia and Maxillopoda, Myriapoda, Pentastoma, Priapula, Phoronida, Ectoprocta, the brachiopod groups Articulata and Inarticulata, the mollusk groups Cephalopoda and Scaphopoda, the annelid groups Polychaeta and Hirudinea, Pogonophora, Sipuncula, Echiura, Nematoda, and Platyhelminthes. We will compare these cladistically, along with many published gene arrangements, as well as compare DNA and inferred amino acid sequences in order to infer evolutionary relationships among higher metazoan groups.
