lamoran at gpu.utcc.utoronto.ca (L.A. Moran) writes:
>You can plug anything you want into "gene X". All such statements have about
>the same scientific legitimacy. Why do some people feel that rRNA genes
>are special in this sense? This is an argument that seems to be widely
>disseminated but rarely questioned. Can anyone supply a reference to an
>article makes the case that rRNA genes cannot be horizontally transferred
>but others can?
Of course all genes be horizontally transfered, in the sense that it
would be physically possible. However, the more interesting question
is "is the copy we see today in the genome derived from a horizontal
transfer event in the past".
Let's consider a prokaryote hundreds of millions years ago that has
just recieved a gene by horizontal transfer. If the horizontally
transfered gene doesn't confer any selective advantage, then why would
the particular organism receiving the copy out of its billions of
sisters be the ancestor of a phylogenetic group we are studing today?
We only see the descendants of the winners of evolution.
So, unless you believe a horizontal transfer of rRNA would confer a
great selective advantage, the chances of rRNA genes today being
derived from a horizontal transfer event in the past are very slim
indeed.
Phylogeny is about evolution. Wherever thinking about it, one needs to
think evolutionarily.
