From Wikipedia,
the free encyclopedia.
Schematic of a region of a
chromosome before and after
a duplication event
Gene duplication occurs
when an error in
DNA replication leads to the
duplication of a region of DNA
containing a (generally
functional)
gene. The significance of this
process for
evolutionary biology is that
if a gene is under
natural selection, many
mutations will lead to loss of
functionality and thus are
selected against. When a gene is
duplicated selection may be
removed from one copy and now the
other gene locus is free to mutate
and discover new functions.
Alternatively, the gene may
acquire deleterious mutations and
become a
pseudogene.
The postulate that gene
duplication has a major role in
evolution was developed in the
1980s and is now widely
accepted as a major evolutionary
force. Some have argued that gene
duplication is the most important
evolutionary force since the
emergence of the
universal common ancestor.
Major
genome duplication events are
not uncommon. It is predicted that
the entire yeast genome underwent
duplication only ~1,000,000 years
ago. Plants are the most prolific
genome duplicators. Wheat for
example is hexaploid (a specific
term for a
polyploid organism) meaning it
has six duplicate copies of its
genome.
The two genes that exists after
a gene duplication event are
paralogs. Paralogs usually code
for
proteins with different
function and/or structure as
stated above. This is opposed to
orthologous genes that code for
proteins with similar function but
that exists in different species.
Orthologs are created from a
speciation event. (See
Homology of sequences in genetics).
It is important (but often
hard) to differentiate between
paralogs and orthologs in
biological research. Experiments
on human gene function can often
be carried out on other
species if a homolog to a
human gene can be found in the
genome of that species. But
only if the homolog is orthologous.
If they are paralogs and resulted
from a gene duplication event
their function is probably too
different.
