Transcript Unit2Day6x
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