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From Genes to Behavior: Outline I I Review of Ridley Gene-environment interactions: norms of reaction I I tanning, geckos, soapberry bugs Violence, MAOA and Upbringing I epigenetics I heritability I Ease of learning: selection shapes what we learn, and when I Garcia: why does a reinforcer reinforce? I What do infants attend to? I Sensitive period learning Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently? Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently? I Vasopressin/oxytocin: hormones promotes social bonding I affects cells only if a receptor for it in the cell I prairie vole has mutation (insertion) in promotor region of receptor gene I changes expression of gene in different parts of brain Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently? I Vasopressin/oxytocin: hormones promotes social bonding I affects cells only if a receptor for it in the cell I prairie vole has mutation (insertion) in promotor region of receptor gene I changes expression of gene in different parts of brain SO: a change in a single gene affects monogamy or polygyny! Discussion of Ridley Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? Discussion of Ridley Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners Discussion of Ridley Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners Do we also need an environmental signal to release vasopressin? Discussion of Ridley Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners Do we also need an environmental signal to release vasopressin? Sex → release of vasopressin → male gets “addicted” to his mate. So environment matters, but a simple response How to think about genes and environment: Norms of reaction norm of reaction: expression of a genotype in different environments Response is shaped by selection, so also evolved “human nature” Norms of reaction: sex ratio in leopard geckos Leopard gecko nature: more males to be born when the temperature is high Norms of reaction: Mate-guarding in Soapberry bugs When is it adaptive for bugs to mate-guard? Norms of reaction: Mate-guarding in Soapberry bugs When is it adaptive for bugs to mate-guard? Gene-culture interaction: Violence, MAOA and Upbringing Violence, MAOA and Upbringing: two reaction norms NOTE: has not always been replicated Epigenetics; How the environment affects gene expression I humans are just under 99 percent genetically identical to chimpanzees I Difference is in which genes are switched on or off in development I liver and skin cells contain same genes; not all expressed. Why? I Epigenome: chemical markers and switches on chromosome that prevent expression. One epigenetic marker is a methyl group (CH3) attached to DNA, silences gene I I I A gene silenced like that is said to be “imprinted” The epigenome is affected by the environment: software to DNA hardware Epigenetics: Diet, BPA and the agouti mice Randy Jirtle and the agouti mice: I agouti mice carries gene that makes them ravenous, diabetic, and yellow I most offspring like their parents I unless fed “special diet” rich in methyl-donors (onions, garlic, beets) I then they had the same gene, but looked brown and healthy I some of those chemicals are in vitamins for pregnant women too What does exposure to BPA do to the agouti mice? Epigenetics: BPA and the agouti mice environmental influences affect gene expression throughout life Epigenetics: Behavior affects the epigenome Michael Meaney: 2 kinds of mother rats I nurturing rat moms (licked babies) had brave, calm babies I neglectful rat moms (didn’t lick) had nervous, fearful babies what is going on in the rat brain? I I I I licking releases serotonin, activates serotonin receptors in hippocampus licked rats have bigger hippocampi, less cortisol rats have same genes, different methylation patterns in hippocampus I is it reversible? yes I Trichostatin (similar to valproate, mood stabilizer) given to adult rats could reverse epigenetic signals behavior can influences gene expression throughout life Epigenetics: What about people? Parenting affects children (in low birthweight babies) I adults with poor relationship with mother: small hippoampi I adults with good relationship with mother: large hippoampi What about grandchildren? I Pembry studied 200 yrs crop yields in Sweden; food availability fluctuated a lot I grandfathers who were young teens in good times had grandsons with diabetes I grandmothers who were babies in good times had granddaughters with diabetes I What happened? sperm formed in teen years, eggs in utero or as infants A brief note on heritability LESSON THUS FAR: WHEN TALKING ABOUT AN INDIVIDUAL, cannot separate genes from environment BUT, WHEN TALKING ABOUT A POPULATION: Geneticists do separate variation due to genes and environment heritability = proportion of phenotypic variance due to genetic variance 1. note: heritability only applies to a population 2. more environmental variance lowers heritability Ease of learning Learning biases: Another view of gene-environment interactions 1. Genes affect what you learn easily 2. Some things are easy to learn, others hard 3. Genes affect what you attend to. . . 4. And what you attend to is what you are likely to learn Ease of learning: Garcia’s experiments Ease of learning: Attention in infants I What you attend to is what you learn: faces are important Ease of learning: Attention in infants Eyes are especially salient. . . Ease of learning: Attention in infants ...Especially when those eyes are looking at you. Summary I Genes don’t do anything unless they are expressed I Epigenetic switches control gene expression I Environment and behavior affect that expression (agouti mice, upbringing) I Reaction norms summarize how a genotype is expressed in different environments I Reaction norms – the response of the gene – is genetic I Genes also affect learning and attention in adaptive ways