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/content/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 Poolall 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.

-Richard Dawkins,The Ancestor's Tale , page 432

Bring in the time dimension, and the pool becomes a river, flowing through geological

time..."

Natural Selection