Appendix 1—Repeat sequences in putative gene PR.C

Ohno argued that removing a specific T nucleotide from gene RIIA (which codes for enzyme EII) leads to a putative predecessor gene PR.C having several short repeat sequences,1 such as those shown in tables 1–5.2 He claimed this showed that putative PR.C arose from a chain of identical oligomers.3

table1
Table 1. Examples of four-codon internal repeats in putative ancestral gene PR.C, and their location.
table2
Table 2. Examples of five-codon internal repeats in putative ancestral gene PR.C, and their location.
table3
Table 3. Examples of six-codon internal repeats in putative ancestral gene PR.C, and their location.
table4
Table 4. Example of seven-codon internal repeats in putative ancestral gene PR.C, and their location.
table5
Table 5. Example of ten-codon internal repeats in putative ancestral gene PR.C, and their location.

Ohno claimed the ancestral PR.C coded for a protein consisting of multiple copies of Arg-Arg-Arg-Ser-Thr-Pro-Leu-Asp-Ala-Ala, which we labelled AA-10 in this paper. He made no attempt to align such a protein with the product from PR.C to explain how the repeats in tables 1–5 could have subsequently arisen.

References and notes

  1. Ohno, S., Birth of a unique enzyme from an alternative reading frame of the pre-existed, internally repetitious coding sequence, Proc. Natl. Acad. Sci. USA 81:2421–2425, 1984. Return to text.
  2. See PR.C internal homologyReturn to text.
  3. Yomo, T., Urabe, I. and Okada, H, No stop codons in the antisense strands of the genes for nylon oligomer degradation, Proc. Natl. Sci. USA 89:3780–3783, 1992. Return to text.