Trichinella spiralis mtDNA: A nematode mitochondrial genome that encodes aputative ATP8 and normally structures tRNAs and has a gene arrangement relatable to those of coelomate metazoansc

The complete mitochondrial DNA (mtDNA) of the nematode Trichinella spiralis has been amplified in four overlapping fragments and 16,656 bp of its sequ ence has been determined. This sequence contains the 37 genes typical of me tazoan mtDNAs, including a putative atp8, which is absent from all other ne matode mtDNAs examined. The genes are transcribed from both mtDNA strands a nd have an arrangement relatable to those of coelomate metazoans, but not t o those of secernentean nematodes. All protein genes appear to initiate wit h ATN codons, typical for metazoans. Neither TTG nor GTT start codons, infe rred for several genes of other nematodes, were found. The 22 T. spiralis t RNA genes fall into three categories: (i) those with the potential to form conventional "cloverleaf" secondary structures, (ii) those with T PsiC arm + variable arm replacement loops, and (iii) those with DHU-arm replacement loops. Mt-tRNA(R) has a 5'-UCG-3' anticodon, as in most other metazoans, in stead of the very unusual 5'-ACG-3' present in the secernentean nematodes. The sequence also contains a large repeat region that is polymorphic in siz e at the population and/or individual level.