Par17 is only encoded by genomic sequences of hominid species. A. Sequence alignment of Par17 sequences. Parvulin exon 1 sequences were PCR amplified from genomic DNA of 10 different primate species. The resulting DNA sequences were aligned with respect to the Par17 and Par14 ATG codons; the respective Bos taurus sequence was obtained from Ensembl and aligned accordingly. Translated protein sequences in-frame with the respective ATG codons are given below the DNA sequences with stop codons written in red. Within the genomic sequences of Homo sapiens and Macaca mulatta (obtained from Ensembl), the Par17 ATG codons are immediately preceded by an in-frame stop codon. The Q16/R18 to R16/S18 coupled SNPs that were described for the human sequence are highlighted in grey; comparison with the other primate sequences reveals the QR form to be the ancestral one. Phylogenetic clades used in scheme B are indicated by boxes here and the respective abbreviations from B. B. Phylogenetic scheme of primate relationships and Par17 sequence features. The Par17 elongation is preformed in sequence in all anthropoid genomic DNAs tested. Additional ATG codons at the putative starting position of Par17 exist in all tested species, but are out-of-frame relative to the Par14 coding sequence in New World and Old World monkeys. The gap of five nucleotides in New World monkeys shrinks to a gap of four nucleotides in Old World monkeys, still preventing a continuous ORF with Par14. The upstream ATG codons are in-frame with the Par14 sequence in the clade of apes, only. Within the gibbon sequence however, an in-frame stop codon prevents expression of an extended protein. This stop codon has been sequenced in three independent clones. Thus, only Hominidae (Homo, Pan, Gorilla and Pongo) possess an extended ORF that can lead to the expression of Par17. (The length of the branches in this scheme does not reflect any phylogenetic distances.) C. Exon 3 sequences were obtained as in A. Exon 3 sequences are highly conserved with only two amino acid substitutions between human and cow or human and mouse, respectively. Amino acid exchanges relative to the human sequence are in white on black. Phylogenetic groupings are indicated by boxes as in A.