Biology Reference
In-Depth Information
return-to-the-sea example from Sec. 2.4. If all marine vertebrates
were grouped together in a reversion polyphylon, on the basis of their
common hydrodynamic morphology, one would mask the fact that
the marine mammals have returned to the sea: the land-dwelling adap-
tation of ancient mammals as well as the following readaptation to sea
of marine mammals are the two masked events. The marine mammals
are wrongly presented as not having evolved at all morphologically,
while they have in fact evolved a lot! They are definitely not fish!
Alternatively, if one grouped all present-day active-flight vertebrates
(birds and bats), as we have seen this would mean creating a convergence
polyphylon, a grouping which would conceal the fact that their cenances-
tor did not fly at all! The fundamental fact that active flight has developed
twice and independently so in the two lineages would be completely
masked. In a way, a convergence polyphylon is even more absurd than a
reversion polyphylon because the very character that has been used to
combine the two lineages into a group is not present at all in their
cenancestor!
5. Uses of Phylogenetics in Molecular Biology
So far, we have seen many sides of phylogenetics, ranging from the
hypothesis of homology to the problems of homoplasy and varying evo-
lutionary rates. We have briey discussed three main classes of algorithms
used for the reconstruction of phylogenetic trees. In this section, we will
shed some light on the role of phylogenetics in molecular biology and
genomics.
5.1. Prediction of Gene Function
A most fruitful use of phylogenetics is in predicting gene function. With
the sequencing of many genomes, including the human one, focus is
shifting towards the identification of genes and the determination of gene
function. While gene function was often known at the time of sequenc-
ing before the large genome projects began, today many sequences are
only surmised to be genes due to the structure of their sequence, and
functions are attributed by comparison with genes in other species.
