Download Gene co-option

Gene co-option
• the process by which a trait/gene changes function; the gene has been
co-opted to do a new job
Gene Co-option
Inheritance of Acquired Characteristics
Epigenetics turns on/off genes
http://cnx.org/content/m26565/latest/graphics35.jpg
Epigenetic patterns are heritable, but can be changed
by the environment more easily than can genes
Jirtle and Skinner, 2007, Nature Reviews Genetics
Epigenetics and behavior
http://learn.genetics.utah.edu/conte
nt/epigenetics/rats/
What explains Darwin’s finches?
Darwin’s finches
Patel, 2006, Nature, 442:515-516
The BMP4 Gene
Same protein
Different mRNA levels
in different species
A second gene…
CaM
Beak morphology
is skeletal and
related to
differences in
CaM expression
during
development
Abzhanov et al., 2006, Nature, 442:563-567
Up or down regulation of two genes can create a
wide variety of 3-D shape
Abzhanov et al., 2006, Nature, 442:563-567
What explains Darwin’s finches?
• Difference in gene expression (high, moderate,
or low) for two genes. What are the possible
mechanisms?
– Switch?
– Gene duplication?
– Epigenetics?
Which do you think is more likely?
• Mutations are accidents within the cell during
DNA replication and during meiosis
• These mutations happen with no regard to
what is happening to the organism or to what
the organism needs…
• That doesn’t mean that some mutations
aren’t lucky!
• Mutation creates new alleles that can be
selected for or against
Mutation is
important in
evolution because
it is THE source of
new alleles
Gene Pool
all of the alleles in
all of the gametes of
the population
•Concept works for sexual
reproducers
•Alleles can unite randomly (as
if swimming), or they can
unite non-randomly if there is
mating preference
Dawkins on “Gene Pools”
“The very idea of a gene pool has no meaning if there is no sex. 'Gene
Pool’ is a persuasive metaphor because the genes of a sexual
population are being continually mixed and diffused, as if in a liquid.
Bring in the time dimension, and the pool
becomes a river, flowing through geological
time..."
-Richard Dawkins,
The Ancestor's Tale , page 432
Natural Selection