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Chapter 1 Evolution, Genetics, and Experience Men commit more violent crimes than women. Why is this? How many of you have ever heard the question: Is it nature, or is it nurture? Is it inherited, or is it learned? Why are those questions flawed? Thinking About the Biology of Behavior Nature-Nurture Debate Nature • Influence of individual's innate qualities *Genetics Nurture • Influence of learning and experience on behavior *Gestation *Stress levels *Sensory stimulation *Nutrition *Parents *Friends *Culture Thinking About the Biology of Behavior Don’ts: • Don’t think in dichotomies of either nature or nurture • Don’t think in terms of proportions of nature/nurture Do’s: • Embrace an Interactive Model • Nature/nurture and physiology/psychology are always interacting! Thinking About the Biology of Behavior What question should we use to replace “Is it nature or nurture?” Evolution Why do we discuss evolution in a biopsychology class? Evolution 1. Similar brain structures 2. Nervous systems functions similarly *Neurons in worms work much like ours 3. We inherited behavioral traits from our ancestors A Metaphor Why do you get “goose bumps” when you are frightened? “When people are frightened they tend to get “goose bumps” – erections of the hairs, especially on their arms and shoulders. Goose bumps are useless to humans because our shoulder and arm hairs are so short. In most other mammals, however, hair erection makes a frightened animal look larger and more intimidating. An evolutionary explanation of human goose bumps is that the behavior evolved in our remote ancestors and we inherited the mechanisms.” –Kalat, p.4 How is genetic material passed on? How does that contribute to genetic diversity? Fundamental Genetics Mendelian Genetics Gregor Mendel Dichotomous Traits • Studied inheritance in pea • Occur in one form or the plants other, never in combination True Breeding Lines • Interbred members always produce offspring with the same trait Do you inherit your traits from you parents? Fundamental Genetics Mendelian Genetics Dominant Trait First Generation • The trait of a • All plants had 1B gene and dichotomous pair that is 1w gene expressed in a phenotype • All plants had brown seeds Recessive Trait Second Generation • Trait of a dichotomous • ¾ plants had brown seeds pair not expressed in the phenotype Fundamental Genetics Mendelian Genetics Phenotype • An organisms observable traits Genotype • Traits that can be passed on through genetic material Chromosomes Reproduction, Linkage, and Recombination DNA • Each chromosome is a double-stranded molecule of DNA • Located in nucleus and mitochondria of cells • Each strand is a sequence of nucleotide bases A, T, G, C A-T C-G Fundamental Genetics Mendelian Genetics Gene • A sub section of a chromosome that controls a characteristic Fundamental Genetics Mendelian Genetics Alleles Alleles • Two genes that control • Located at the same locus the same trait of a pair of chromosomes Fundamental Genetics Mendelian Genetics Homozygous • Organisms that posses two identical genes for a trait Heterozygous • Two dif. genes for a trait How is genetic diversity achieved? How are natural selection and genetics related? Chromosomes Reproduction, Linkage, and Recombination Chromosomes • Threadlike structures in the cell nucleus that contain the genes • Each chromosome is a DNA molecule Chromosomes Reproduction, Linkage, and Recombination Gametes • Egg cell, sperm cell • Has ½ the number of chromosomes *23 *All other cells have 23 pairs Chromosomes Reproduction, Linkage, and Recombination Meiosis • Process of cell division that produces four gametes • Accounts for much of the genetic diversity • For each pair you can get one from mom or one from dad • 23 to the 23rd = 8,388,608 Chromosomes Reproduction, Linkage, and Recombination Linkage • The tendency for traits that are encoded on the same chromosome to be inherited with each other Chromosomes Reproduction, Linkage, and Recombination Crossing Over • During meiosis the chromosomes replicate, line up, then cross over and split off • Occurs at a random point • Increases diversity – shuffles the “genetic deck” Chromosomes Reproduction, Linkage, and Recombination Mutations • Accidental alterations in individual genes • Rare, but can lead to rapid evolution How do the genes and environment interact to influence characteristics and behavior? Genetic Expression Main Ideas • Multiple genes interact to produce complex characteristics • Genes indirectly influence characteristics • The environment plays a critical role in gene expression Gene Expression Gene Expression • There are no genetic effects without the expression of a gene • Gene “expression states” are heritable “Environments cannot influence gene sequences but they can and do influence gene expression.” - Rutter, Moffitt, and Caspi (2006) Gene Expression Development of Birdsong • In songbirds, areas of the brain that are responsible for producing song are much larger in males than females (because of testosterone) • Male birds that sing are born with genetics to acquire the song of their species. Gene Expression Development of Birdsong • Typically, when male birds are born they hear the song sung by older adults – even though they cannot sing at this point • If they do not hear the song of their species during the critical developmental period after birth they typically do not acquire the song * If they acquire a song it is usually abnormal Gene Expression Structural Genes • Genes that contain info necessary for the synthesis of types of proteins • All cells in the body contain exact same structural genes • The processes of building proteins from DNA can be influenced by the environment Gene Expression Operator Genes • Control structural genes • Like switches – regulate which genes will make proteins an at what rate • Determines what type of cell it will be (blood cell, brain cell, liver cell, etc.) Video: Lecture 2_NOVA_Can We Live Forever? 19:30-30:00 Gene Expression Epigenetics “A key feature of gene expression is that it can be altered in a reversible way by extra-cellular signals and by environmental influences. Although DNA starts off the causal chain, what really matters is the expression of the genes (in terms of messenger RNA). There are no genetic effects without this expression. Unlike the operation of DNA, which is active in all cells, gene expression tends to be specific to particular body tissues and to particular phases of development. This class of mechanisms has been called epigenesis.” - Rutter, Moffitt, and Caspi (2006) Gene Expression Epigenetics Epigenetics Epigenetics • Environment influences • Plays a major role in gene molecules (proteins) that expression bind to the DNA (on top of it) • Accumulate throughout life • DNA-binding Proteins regulate operator genes (turn them on, off, up, down) Gene Expression Epigenetics Epigenetics DNA-Binding Proteins • Epigenomes do not affect Methylation – turn genes off DNA, but are heritable (can Histone Acetylation – turn be passed on to at least one genes on generation) Gene Expression Final Thoughts The Environment: • Cannot alter the genes you have • Can alter the expression of the genes you have • Can alter your epigenome • And your epigenome IS heritable • Thus, environmental influences of genetic expression ARE heritable, but only through the EPIGENOME Factors that Influence Epigenetic Patterns • Prenatal environment (nutrition, hormones, etc) • Smoking • Diet • Stress • Physical activity • Epigenetic drift – naturally occurring changes through successive cell divisions Video http://www.pbs.org/wgbh/nova/body/epigenetics.html Behavioral Development: Gene-Environment Interaction Maze-Bright, Maze-Dull Rats • Tyron (1934) demonstrated that traits can be selectively bred • Trained heterogeneous group of rats • Mated rats with least mistakes and ones with most mistakes (for many generations) • By 8th gen. almost no overlap between groups • Included cross-fostering control • Are there any potential confounds to this study? Behavioral Development: Gene-Environment Interaction Maze-Bright, Maze-Dull Rats Confound 1: Parenting Cross-fostering: Maze-bright offspring raised by mazedull parents Confound 2: Extraneous traits • Searle (1949) tested rats on 30 dif. behavioral tests • Maze-dull rats not less intelligent, but more emotional Behavioral Development: Gene-Environment Interaction Maze-Bright, Maze-Dull Rats Gene-Environment Interaction • Both groups raised in: *Enriched environment *Impoverished environment Behavioral Development: Gene-Environment Interaction Maze-Bright, Maze-Dull Rats Gene-Environment Interaction • Both groups raised in *Enriched environment *Impoverished environment • Both groups performed equally well when raised in an enriched environment