Doug Eernisse (DEernisse at fullerton.edu) wrote:
: In article <3v7ujo$1m8 at decaxp.harvard.edu>, robison at lipid.harvard.edu: (Keith Robison) wrote:
: > HPYockey (hpyockey at aol.com) wrote:
: > : Chapter 7 of my book Information theory and molecular Biology discusses
: > : the evolution of the standard triplet genetic code from a primitive
: > : doublet code. The mathematical background needed to understand the
: > : argument is in Part I of this book.
: > : Chapter 7 shows that if the primeval genetic code had a vocabulary of
: > : fewer than 20 amino acids, for example perhaps 8, then there should have
: > : evolved about 10 separate codes. These are the mitochondrial genetic codes
: > : usually regarded as minor differences from the standard genetic code.
: > : When you read Chapter 7 please e-mail me any comment or questions.
: > Disclaimer: I haven't read your book (time to go to library :-)
: > The main problem with this hypothesis is that the phylogenetic
: > distribution of non-standard genetic codes doesn't support this
: > very well -- the non-standard codes show up all over the tree,
: > and not just in mitochondria. I think Thomas Jukes and coworkers
: > have made a pretty strong argument that the non-standard codes
: > are a recent, derived phenomenon rather than an ancient relic.
: I agree with Keith, except that all the non-standard codes I know about are
: restricted to mitochondrial DNAs.
Other examples (from memory; don't have my copies of cites handy)
Cilliate nuclear DNA
Some mycoplasmas (bacteria)
Very new reference on cilliate nuclear code deviations
BAROIN-TOURANCHEAU-A. TSAO-N. KLOBUTCHER-L-A. PEARLMAN-R-E.
Genetic code deviations in the ciliates: evidence for multiple and
EMBO-J. 1995 JULY 3. 14(13). P 3262-3267.
Good reference, though getting old
Recent evidence for evolution of the genetic code.
Osawa S; Jukes; TH; Watanabe K; Muto A
Microbiol Rev 56: 229-264 (1992)
: Are there non-mtDNA examples that I am missing, or are any of the
: above deviations no longer accepted?
: Keith's point is still valid, especially if these mtDNAs all had a common
: origin from a eukaryotic ancestral mtDNA that had standard coding
: (references on early diverging eukaryotic lineages whose mtDNAs have
: standard coding would also be appreciated).
Well, I think the phylogenetic evidence pretty clearly places the
mitochondria in the purple bacteria, which all use the standard code.
Department of Cellular and Developmental Biology
Department of Genetics / HHMI
robison at mito.harvard.edu