Evolution by Natural Selection average phenotype changes environment Allele frequencies unfavorable for blue change Evolution w/o Selection average phenotype changes Drift rare alleles lost stochastic events Allele frequencies change Migration new alleles (genes) (gene flow) present gene flow from neigh- Allele frequencies bor population (species) change new alleles (genes) Mutation present Vp = Vg + Ve SNP, duplication, Allele frequencies deletion, etc. change Selection w/o Evolution selection between generations Development NO new alleles Plasticity Allele frequencies environment are unchanged unfavorable rounded phenotypes • Some phenotypic variants are favored by selection, they survive and reproduce better • But there is no genetic basis to this variation, the individuals with greater fitness have good luck rather than good genes GOAL: understand the genetic underpinnings of Behavior Singe gene vs. quantitative trait. Genes that are necessary for: Genes that Contribute to: Single Gene Quantitative or many genes Historic figure Mendel Galton identify dominant & recessive identify single genes define Genomic Architecture define mechanisms Immediate goals (#, location, interaction, specificity, linkage) quantify variation in a population describe change in gene frequency Sever disruptions Raw Materials used Lab induced (white coat) Subtle variation Naturally occurring (rubber boot) Tools us ed Bottom Up Forward Top D ow n ( = F or w ar d) Phenotype >>> Gene Observational mutagenesis/screening Comparative Genomics transgenesis Association mapping (GWAS) Reverse Experimental Gene >>> Phenotype artificial selection Knockout crossing (artificial or natural population) RNAi QTL mapping Type of Result Recombinant inbred lines Essential genes of behavior Association Studies (newer techniques are more subtle) Genes that Contribute to Behavior Factors, epistasis, GXE, probability What observations or experiments can be used to partition phenotypic variance into its genetic and environmental components? Vp = Vg + Ve Don’t write here Heritability: the proportion of the phenotypic variance that is due to genetic variance h2 = Vg Vp a measure of dispersion from the mean Don’t write here Heritability, Exploratory Behavior, Great Tits - noted where a bird was at each second in time - noted flights and hops between locations. - total number of flights and hops within the first 2 min = ‘exploratory score’ Don’t write here (Dingemanse et al., 2002, Anim. Behav) Heritability, Exploratory Behavior, Great Tits • h2 parent offspring regressions were 0.22-0.41 • h2 sibling analyses 0.37-0.40 estimate heritability as the slope of parent/offspring correlation Don’t write here (Dingemanse et al., 2002, Anim. Behav) estimate heritability as the slope of parent/offspring correlation migration timing is heritable & selectable Pulido et al (2001) PRS 268:953-959. S Note: the value for Heritability: Heritability changes as The genetic variance in the Population changes R S R Don’t write here estimate heritability as response to selection divided by the strength of selection h2 = R S AaBb aaBb VA VD VI estimate heritability generally capture the additive genetic variation Components of Genetic Variance (Vg) examples of classical and modern behavioral assays used for screening drosophila mutants for behavioral genetics note the power of high throughput techniques. Eclosion/activity Writing space Don’t write here Seymour Benzer: single gene Molecular Clock in Drosophila Don’t write here Not all drosophila assays are high throughput Dunnock Writing Writing space space Don’t write here Dunnock Writing Writing space space Vasopressin Oxytocin injection of AVP injection of OT facilitates pair bond facilitates pair bond formation in male formation in female monogamous voles monogamous voles Don’t write here Monogamous Promiscuous Don’t write here Autoradiography Viral vector to increase V1aR Don’t write here Promiscuous Monogamous Behavior Promiscuous Monogamous Don’t write here Behavior Promiscuous Monogamous Genetic Marker Promiscuous Monogamous Don’t write here note mismatch of genotypes and phenotype called into question the causal relationship Dunnock Shorter (montane vole-like) Longer (prairie vole-like) Amygdala & hippocampus shorter Writing Writing space space longer within species variation parallels between species Artificially selected (based on genotype) prairie vole lines Don’t write here Genetic markers A genetic marker is an alteration in the genomic DNA (polymorphic) that can be observed (by either sequence or phenotypic result) with a known location on a chromosome. A genetic marker can be used to identify whether an individual has certain genomic DNA at this location. Don’t write here X 70 X X X X X X X 10 100 100 30 Phenotype score Phenotype Phenotype Association l l l l l Statistical 0 5 10 15 20 Generation Two camps QTL Studies – Writing Writing space space Don’t write here Requirement # 1: strains with different phenotypes Requirement #2 : genetic markers Requirement #3 : ability to cross Two camps QTL Studies – Top Down Writing Writing space space Don’t write here P. man icu lat u s P. p o lio n o t u s Hopi Hoekstra Freq. w/ escape tunnel length tunnel escape w/ Freq. 526 loci surveyed w/ Rad-seq 272 backcross mice assayed isogenic lines or recombinant inbred lines capture some of the natural genetic variation but allow you to retest stocks for which genome sequence info may be available. Don’t write here.