BIOPSYCH chp2.pdf

Both within & between species No psychosurgery should be done without detailed assessment of the surgery effects on large sample o Psychosurgery: any brain s...

Both within & between species No psychosurgery should be done without detailed assessment of the surgery effects on large sample o Psychosurgery: any brain surgery performed for the treatment of a psychological problem Patients judged to be improving if they were more manageable Moniz and others failed to carefully evaluate the consequences of the surgery in the first patients to undergo the operation for prefrontal lobotomy Patients were frequently judged as improved if they were more manageable Impressions that the operation was therapeutically effective were based on the physicians who had prescribed the surgery, not the patients LECTURE 2 – Evolution, Genetics, & Experience Zeitgeist: the general intellectual climate of our culture o Promotes ways of thinking abt the biological bases of behavior that are inconsistent with the facts Thinking about the Biology of Behavior: From Dichotomies to Interactions Describe the origins of the physiological-psychological & nature-nurture ways of thinking Explain why thinking about the biology of behavior in terms of traditional physiological-psychological & nature-nurture dichotomies is flawed ----------------------------------------------------------------------------------------------------------------- The Origins of Dichotomous Thinking o Dichotomy: simple way of thinking ▪ Good-bad, right-wrong, good-bad, attractive-unattractive o Tendency to think abt behavior in terms of dichotomies illustrated by 2 kinds of questions asked abt behavior ▪ IS IT PHYSIOLOGICAL, OR IS IT PSYCHOLOGICAL? Emerged in Europe in the 17th century as modern science, a lot of the new scientific knowledge went against what the Catholic Church dictated  The French philosopher Rene Descartes (day-cart) came up with a solution o Cartesian Dualism: the separation of mind & body ▪ Physical matter: behaves according to the laws of nature & is a suitable object for scientific investigation The human body, including the brain, & nonhuman animals ▪ Human mind: the soul, self, & spirit, which lacks physical substance, controls human behavior, obeys no natural laws, & is influenced by the Church o Gave one part of the universe to science & the other part to the Church ▪ IS IT INHERITED, OR IS IT LEARNED? Debate on whether the behavior of humans & other animals is inherited or acquired through learning o This debate is commonly known as the nature-nurture issue John B. Watson, the father of behaviorism, was on nurture’s side North American experimental psychology o Ethology: the study of animal behavior in the wild o On nature’s side European ethology o Instinctive behaviors: behaviors that occur in all like members of a species, even when there seems to have been no opportunity for them to have been learned o Emphasized the role of nature, or inherited factors in behavior ▪ Instinctive behaviors aren’t learned, early ethologists assumed they are entirely inherited AND THEY WERE WRONG NAURRRRRR Problems with Thinking about the Biology of Behavior in Terms of Traditional Dichotomies o Problems with Physiological-or-Psychological Thinking ▪ Julien Offray de la Mettrie argued that thought was produced by the brain ▪ Both arguments deal with self-awareness which is a hallmark of the human mind ▪ ARGUMENT 1 Even the most complex psychological changes can be produced by damage to, or stimulation of, parts of the brain o Changes in self-awareness, memory, or emotion ▪ Oliver Sack’s (1985) “The Man Who Fell Out of Bed  Asomatognosia: a deficiency in the awareness of parts of one’s own body  Typically involves the left side of the body & usually results from damage to the right frontal & parietal lobes o This is cuz we have cross functioning ▪ ARGUMENT 2 Some nonhuman species, particularly primate species, possess some abilities that were once assumed to be purely psychological & thus purely human o Complex problem solving  The Case of the Chimps with Mirrors by Gallup (1983) Chimps used the mirror to groom, inspect parts of its body, & experiment with its reflection by making faces Each chimpanzee was anesthetized, & its eyebrows was painted with a red, odorless, dye Upon seeing its painted eyebrow in the mirror, each chimpanzee repeatedly touched the marked area on its eyebrow while looking in the mirror Many other species passed this mirror self-recognition test  o Asian elephants, orangutans, & European magpies Humans pass this test once we read 15 to 24 months of age o Problems with Inherited-or-Learned Thinking ▪ ARGUMENT 1 Many factors other than genetics & learning were shown to influence behavioral development o Fetal environment, nutrition, stress, & sensory stimulation o Asymmetry of the brain: brain parts are of different sizes ▪ Lesser & weaker neuronal pathways o Nurture now encompasses learning and environment o Changed the nature-or-nurture dichotomy from “genetic factors or learning” to “genetic factors or experience” ▪ ARGUMENT 2 Behavior always develops under the combined control of both nature & nurture o Behavioral development is through the interaction of genetics & experience ▪ Interactionism: behavior is best viewed as the product of genetic potential interacting with past experience & current situational factors  You learn to tolerate with stress and build a higher tolerance for it o A Model of the Biology of Behavior  ▪ All behavior is the product of interactions among 3 factors The organism’s genetic endowment o Which is a product of its evolution Experience Perception of the current situation Human Evolution Describe the origins of evolutionary theory Explain the evolutionary significance of social dominance & courtship displays Summarize the pathway of evolution from single-cell organisms to humans Describe 9 commonly misunderstood points about evolution Describe how research on the evolution of the human brain has changed over time ----------------------------------------------------------------------------------------------------------------- Darwin’s Theory of Evolution o Charles Darwin (1859) publishes On the Origin of Species & modern biology is born o Darwin was not the first to suggest that species evolve from preexisting species ▪ Evolve: undergo systematic change  o He was the first to provide strong evidence & to suggest how evolution occurs ▪ Provided 3 kinds of evidence Documented the evolution of fossil records through progressively more recent geological layers Described striking structural similarities among living species which suggested that they had evolved from common ancestors o A human’s hand, a bird’s wing, & a cat’s paw Pointed to the major changes that had bene brought abt in domestic plants & animals by programs of selective breeding o Most convincing evidence = direct observations of rapid evolution in progress ▪ Grant (1991) observed evolution of the finches of the Galapagos Islands after only a single season of drought Beak size increased in response to shortage of small seeds o Darwin argued that evolution occurs through natural selection ▪ Survival of the fittest ▪ Natural selection: heritable traits associated with high rates of survival and reproduction are the most likely ones to be passed on to future generations ▪ Fitness: the ability of an organism to survive & contribute its genes to the next generation o The evidence for the theory of evolution is unassailable; it meets with no significant opposition from the biological community Evolution & Behavior o Early structure of evolution focused on structure, but behaviors contribute to “fitness” ▪ Behaviors that play obvious roles Finding food Avoiding predation Sexual behavior for reproduction ▪ Behaviors that play a role that is less obvious Social dominance o Many male species establish a stable hierarchy of social dominance through combative encounters with other males  o Why is social dominance an important factor in evolution? ▪ Dominant males copulate more than nondominant males & thus are more effective in passing on their characteristics to future generations  McCann (1981) studied the effect of social dominance on the rate of copulation in 10 bull elephant seals o The dominant male accounted for 37% of the copulations; the lowest ranking accounted for only 1% ▪ In some species, dominant females are more likely to produce more & healthier offspring  Pusey, Williams, & Goodall (1997) found that high-ranking female chimpanzees produced more offspring & that these offspring were more likely to survive to sexual maturity Courtship displays o Courtship displays precedes copulation in many species o Male approaches the female & signals his interest ▪ Signals may be olfactory, visual, auditory, or tactual o Copulation is unlikely if one partner fails to respond appropriately to the signals of the other o Courtship displays are important to evolution cuz they can promote the formation of new species o Species: a group of organisms reproductively isolated from other organisms ▪ The members of a species can produce fertile offspring only by mating with members of the same species o The evolution of an idiosyncratic courtship display can form a reproductive barrier that is as effective as geographical separation   A few birds may fly to a remote island where their descendants only breed with each other. Over many generations, this isolation can lead to the birds evolving into a new species.  A new species can be formed through behavior changes o If some birds start using different courtship displays, these differences can prevent them from mating with the rest of their species ▪ Conspecifics: members of the same species o Only birds with matching courtship behaviors will mate with each other, eventually leading to the development of a new species. Course of Human Evolution o Evolution of Vertebrates ▪ 600 million years ago Complex multicellular water-dwelling organisms first appeared on earth ▪ 450 million years ago First chordates evolved o Chordates: animals with dorsal nerve cords ▪ Large nerves that run along the center of the back or dorsum ▪ 425 million years ago The first chordates with backbones (spinal bone) to protect their dorsal nerve cords Backbone: vertebrae Chordates that possess them are vertebrates First vertebrates were primitive bony fishes o Evolution of Amphibians ▪ 410 million years ago Bony fishes leave the water Fishes that could survive on land for brief periods of time had 2 advantages  o Could escape from stagnant pools to nearby fresh water o Could take advantage of terrestrial food sources Natural selection made the fins & gills of bony fishes transform into legs & lungs Walking catfish evolved into frogs o Evolution of Reptiles ▪ 300 million years ago First reptiles evolved from amphibians First vertebrates to lay shell-covered eggs & to be covered by dry scales o These adaptations reduced the reliance of reptiles on watery habitats ▪ Spends the first stage of life in the watery environment of a shell-covered egg ▪ Once hatched, can live far away from water cuz its dry scales greatly reduce water loss through its water-permeable skin o Evolution of Mammals ▪ 180 million years ago During the age of dinosaurs, a line of reptiles evolved Developed mammary glands to feed their young o How they got the name mammals Stopped laying eggs & instead nurtured their young in the watery environment of their bodies until the young were mature enough to be born o Platypus is one of the surviving mammalian species that lays eggs ▪ Today, there are abt 30 different orders of mammals The one we belong to is primates o Primates: first or foremost There are 12 different families of primates 5 of the most widely studied are the prosimians, old-world monkeys, new-world monkeys, apes, & hominids o The hominid family consists of 2 genera ▪ Homo & Australopithecus  ▪ Apes (gibbons, orangutans, gorillas, & chimpanzees) are thought to have evolved from a line of Old World monkeys SIMILARITIES o Long arms o Grasping hind feet o Specialized for arboreal (treetop) travel o Opposable thumbs that are not long enough to be of much use for precise manipulation DIFFERENCES o Apes have no tails & can walk upright for short distances o Old World monkeys have tails & cannot walk upright ▪ Chimpanzees are the closest living relatives of humans Almost 99% of genes are identical o Emergence of Humankind ▪ Humans belong to the family hominin, genus Homo ▪ First homo species emerged from Australopithecus Australo: southern; pithecus: ape ▪ Australopithecines were only 1.3 meters (4 feet) tall, & had small brains, they had an upright walk & became extinct about 1 million years ago ▪ 2 million years ago First homo species evolved from Australopithecus Homo species size of brain cavity was larger than Australopithecus but smaller than modern humans Early homo species used fire & tools ▪ 6 genera under Homini (tribe) which includes humans: Australopithecus Paranthropus Sahelanthropus Orrorin Pan Homo = got 8 species. o 7 out of 8 extinct. Left Homo Sapiens Thinking about Human Evolution o 9 commonly misunderstood points abt evolution ▪ Evolution does not proceed in a single line ▪ We do not represent evolutionary supremacy We are the last surviving species of a group that has existed for only a brief period ▪ Rapid evolutionary changes do occur Can be triggered by sudden changes in the environment or by adaptive genetic mutations Still a matter of debate among paleontologists o Paleontologists: those who scientifically study fossils ▪ Fewer than 1% of all known species are still in existence ▪ Evolution does not necessarily result in perfect design ▪ Not all existing behaviors or structures are adaptive Spandrels: incidental nonadaptive evolutionary by-products o Our belly button, a nonfunctional by-product of the umbilical cord o Behaviors or structures that were once adaptive might become nonadaptive or even maladaptive if the environment changes ▪ Not all existing adaptive characteristics evolved to perform their current function Exaptations: evolved to serve one function but now do smtg else o Bird wings are limbs that initially evolved for the purpose of walking ▪ Humans are not a single product of ancestral population from Africa We are the combined offspring of many Homo populations that once coexisted & interacted ▪ Similarities among species do not necessarily have common origins Homologous structures: structures that are similar cuz they have a common evolutionary origin Analogous structures: structures that are similar but do not have a common evolutionary origin o Different evolutionary origin Convergent evolution: similarities between analogous structures o Causes analogous structures  o Evolution of different species but uses similar solutions as demanded by the environment ▪ Bird wing & human arm have a basic underlying commonality of skeletal structure that suggests a common ancestor Homologous structure ▪ Bird wing & bee wing have few structural similarities, but both evolved cuz of the common advantage of flight Analogous structure Evolution of the Human Brain o Brain size is not correlated with intelligence ▪ 2 problems Humans don’t have the largest brains o Whales & elephants brains weigh between 5k to 8k grams while ours weigh abt 1350 grams Brain sizes of acclaimed intellectuals were found to be unremarkable ▪ Brain size is correlated with body size o More reasonable approach to the study of brain evolution is to compare the evolution of different brain regions ▪ It has been informative to consider the evolution of the brain stem separately from the evolution of the cerebrum (cerebral hemispheres)  Brain stem: regulates reflex activities that are critical for survival such as heart rate & respiration Cerebrum: involved in more complex adaptative processes such as learning, perception, & motivation ▪ Convolutions lead to a larger cerebrum (helps compact more functions of the brain) ▪ Relative sizes of different brain regions are important to help differentiate our different abilities o 3 points abt the evolution of the human brain ▪ The brain has increased in size during evolution ▪ Most of the increase in size has occurred in the cerebrum ▪ An increase in the number of convolutions has greatly increased the surface area of the cerebral cortex Convolutions: folds on the cerebral surface Cerebral cortex: outermost layer of cerebral tissue o Similarities between the brains of different species are more significant than the differences between them ▪ All brains are constructed of many neurons, similar neural structures can be found in the same locations in other species, performing similar functions Evolutionary Psychology: Understanding Mate Bonding o Evolutionary psychology seeks to understand human behaviors by considering the pressures that led to their evolution o Much attention has focused on a comparison of promiscuity & the less common strategy of mate bonding ▪ Promiscuity: a mating arrangement in which the members of both sexes indiscriminately copulate with many different partners during each mating period ▪ Mate bonding: some male & females species form enduring mating relationships with members of the other sex o Most mammals form mating bonds ▪ Influential theory by Trivers (1972), female mammals give birth to small numbers of helpless, slow-developing young. As a result, it’s adaptive for males to stay with the females who are carrying their offspring & to promote the successful development of those offspring ▪ Male mammals that behave this way are more likely to pass on heritable characteristics to future generations  Natural selection promoted the evolution in mammalian males of the tendency to bond with females with which they have copulated Selection pressure on female mammals to behave in ways that will induce males to bond to them improves their ability to pass on their own heritable characteristics to future generations o Most mammals form polygynous mating bonds ▪ Polygyny: Male mate with multiple females ▪ Evolved as the predominant pattern of mate bonding in mammals Cuz females make a far greater contribution to the rearing of their young than males Mammalian fathers contribute to reproduction ▪ Consequence is females can only produce a few offspring whereas males have the capacity to make many offspring It’s important that female mates with particularly fit males o Increases the likelihood that her offspring will be fit & pass on her genes, along with those of her mate to the next generation ▪ The tendency to establish mating bonds with only the fittest males evolved in females of many mammalian species o The contributions of the males to reproduction are greater than those of females ▪ Polyandry: Female mate with more than one male ▪ Does not occur in mammals Female seahorse deposits her eggs in the male’s pouch, & he fertilizes them & carries them until they are mature enough to venture out on their own o Humans generally form monogamous bonds ▪ Monogamy: mate-bonding pattern between 1 male & 1 female Behavioral change for each female to drive other females of reproductive age away from her mate Fit male bond with a fit female to put most of his reproductive effort into her & their offspring Adaptive in allowing more attention to survival of children o Mate bonding in humans predicted by evolutionary psychology  ▪ Men value youth & attractiveness in their mates more than women do Both indicators of fertility ▪ Women value power & earning capacity more than men do ▪ Physical attractiveness best predicts which women will bond with men of high occupational status ▪ Major mate-attraction strategy of women is increasing their physical attractiveness ▪ Major mate-attraction of men is displaying their power & resources ▪ Men are more likely than women to commit adultery Questions o There has been a long-standing debate on whether humans & other animals inherit their behavioral responses or acquire them through learning. This is called the nature-nurture debate. o The condition that can result from damage to the right parietal lobe & typically involves a lack of awareness of one’s own body parts (most commonly on the left side) is known as asomatognosia. o Darwin proposed that the striking similarities among living species were evidence that they shared a common ancestor. o Through selective breeding programs, major changes have been made to domestic animals & plants. o In some species, the dominant male is likely to copulate more &, therefore, pass on his genes to the future generations. o One distinctive feature of early Homo species was that they had brains larger than Australopithecus but smaller than modern humans. o Incidental nonadaptive evolutionary by-products such as the belly button are called spandrels. o During the course of the vertebrate evolution, birds emerged approximately 160 million years ago. o The overall human brain size does not predict intelligence. o Over millions of years, there has been a remarkable increase in the surface area of the cerebral cortex, the outmost layer of the cerebral tissue in humans. o Evolutionary psychologists suggest that male-female bonding during copulation ensures that the offspring will survive, reproduce, & pass on their genes to the next generation. o Analogous structures are similar because of convergent evolution. Fundamental Genetics pg59  Explain how Mendel’s work with pea plants has informed us about the mechanisms of inheritance Understand the structure & function of chromosomes Describe the process of gene expression Discuss several ways in which modern advances have changed our understanding of genetic processes Define epigenetics, & explain how it has transformed our understanding of genetics ----------------------------------------------------------------------------------------------------------------- Mendelian Genetics o Gregor Mendel is an Augustinian monk o Dichotomous traits: characteristics that occur in 1 form or another, never in combination ▪ Seed color is a dichotomous pea plant trait, every pea plant has either brown or white seeds o True-breeding lines: interbred members will always produce offspring with the same trait generation after generation o Mendel studied dichotomous traits in true-breeding lines of pea plants ▪ Key finding: When true-bred brown & white peas are crossed, all the offspring from the first cross have brown seeds, whereas 25% of the offspring from the second cross have white seeds; this disproved the prevalent view that offspring inherit their parents' exhibited traits ▪ Dominant trait: appear in 100% of the first-generation offspring ▪ Recessive trait: appear in 25% of the second-generation offspring ▪ Phenotype: an organism’s observable traits ▪ Genotype: genetic traits passed on to offspring o 4 central ideas of Mendel’s theory to explain his results ▪ 2 kinds of inherited factors for each dichotomous trait A brown-seed factor & a white-seed factor control seed color o Each inherited factor is called a gene ▪ Proposed that each organism possesses 2 genes for each of its dichotomous traits Each pea plant possesses either 2 brown-seed genes, 2 white- seed genes, or one of each o 2 genes that control the same trait are called alleles Homozygous: organisms that possess 2 identical alleles o 2 white-seed alleles (ww)  Heterozygous: organisms that possess different alleles o 1 white-seed allele & 1 black-seed allele (Bw) ▪ Proposed that 1 of the 2 kinds of genes for each dichotomous trait dominates the other in heterozygous organisms Pea plants with a brown-seed gene & a white-seed gene always have brown seeds cuz brown-seed gene is dominant trait ▪ Proposed that for each dichotomous trait, each organism randomly inherits 1 of its “father’s” 2 factors & 1 of its “mother’s” 2 factors Chromosomes o 2 key aspects of chromosomal function – recombination & replication ▪ Reproduction & Recombination Genes are located on chromosomes which was found during early 20 th century o Chromosomes: threadlike structures in the nucleus of each cell Chromosomes occur in matched pairs in all multicellular organisms Humans have 23 pairs of chromosomes, with an allele on each chromosome Meiosis: the process of cell division that produces gametes (egg & sperm cells) o Chromosomes divide, 1 chromosome of each pair goes to each of the 2 gametes that result from cell division  o Result: each gamete has only half the usual number of chromosomes, & when a sperm & egg cell combine during fertilization, a zygote is produced with full 23 pairs of chromosomes o Genetic recombination: crossover of chromosomes to exchange genetic material ▪ Creates diversity Mitosis: all other cell division in the body ▪ Structure & Replication Each chromosome is a double-stranded molecule of deoxyribonucleic acid (DNA) Each strand is a sequence of nucleotide bases attached to a chain of phosphate & deoxyribose o 4 nucleic bases: adenine, thymine, guanine, cytosine Nucleotides on strand 1 always pair with specific nucleotides on strand 2 Replication: a critical process of the DNA molecule o Mitotic cell division won’t be possible without it o  Sometimes chromosome replication errors can have clinical consequences o Commonly, errors in replication take the form of mutations ▪ Mutations: alterations of individual genes o Disappear from the gene pool within few generations cuz organisms that inherit them are less fit o Sometimes mutations increase fitness & in doing so encourages rapid evolution ▪ Sex Chromosomes & Sex-Linked Traits Autosomal chromosomes: typical chromosome that comes in matched pairs Sex chromosomes: the pair of chromosomes that determines an individual’s sex o Females have XX chromosomes o Males have XY chromosomes o Sex-linked traits: traits influenced by genes on the sex chromosomes ▪ All controlled by genes on the X chromosome cuz Y chromosome is small & carries few genes o Dominant sex-linked traits on the X chromosome will be seen more commonly in females o Recessive sex-linked traits on the Y chromosome more commonly in males ▪ Color blindness Genetic Code & Gene Expression o Structural genes: contain information for the synthesis of proteins o Proteins: long chains of amino acids ▪ Control the physiological activities of cells & are important components of cellular structure ▪ Structural genes compose a small portion of each chromosome & produce diff kinds of cells Hair cells, brain cells, bone cells o Stretches of DNA that lack structural genes include portions called promoters / enhancers ▪ Promoters / Enhancers: determine whether particular structural genes are converted into proteins through a 2 phase process called gene expression ▪ Control of gene expression by promoters is an important process cuz it heavily influences how a cell will develop & function once it is mature ▪ Promoters can be regulated in 2 ways Turned up o Activators: proteins that bind to DNA & increase gene expression Turned down o Repressors: proteins that bind to DNA & decrease gene expression ▪ Gene expression involves 2 phases 1st Phase – Transcription (DNA base-sequence code to RNA base-sequence code) o Strand of DNA unravels & serves as a template for the transcription of a short strand of RNA o Ribonucleic acid (RNA): contains the nucleotide base Uracil instead of Thymine & has a phosphate & ribose backbone instead of a deoxyribose backbone o Messenger RNA: the strand of transcribed RNA ▪ Carries the genetic code out of the nucleus of the cell 2nd Phase – Translation (RNA base-sequence code to protein) o Messenger RNA attaches to any one of the many ribosomes present in the cell’s cytoplasm o Ribosome moves along the strand of messenger RNA, translating the genetic code as it proceeds o Codon: 3 consecutive nucleotide bases along the messenger RNA strand ▪ Instructs the ribosome to add 1 of the 20 diff kinds of amino acids to the protein it’s constructing o Each kind of amino acid is carried to the ribosome by molecules of transfer RNA  ▪ Ribosome read codon -> transfer RNA attaches to the appropriate amino acid on messenger RNA -> once reaches codon that tells ribosome to stop, the completed protein is released into the cytoplasm ▪ Human Genome Project (1990) o Purpose: compile a map of the sequence of all 3 billion nucleotide bases that compose human chromosomes o 3 major contributions ▪ Using this new technology, genomes have already been established for many species, including those of many long-extinct species, leading to important insights into evolution ▪ Humans have about 21,000 structural genes; mice have about the same number, and corn has many more. Indeed, protein-encoding genes constitute only about 1% of human DNA. Human proteome: a nearly complete map of the entire set of proteins encoded for by our genes ▪ So many genes have been linked to each disease that it has proven difficult to sort out the interactions among the numerous genes and experience. Compounding the problem is that even when many genes have been linked to a disease, all of them together often account for only a small portion of its heritability 18 different gene variants have been linked to adult-onset diabetes, but these 18 variants account for only 6% of the heritability of the disease Modern Genetics: Growth of Epigenetics o Epigenetics (1942): focuses on mechanisms that influence the expression of genes without changing the genes themselves o 4 factors that led to the rise of epigenetics ▪ Human Genome Project had generated new research techniques  ▪ Discovered that protein coding genes constitute only abt 1% of human DNA 99% of the synthesis is junk DNA ▪ Most RNA molecules were small Only 1.2% were of the large protein-encoding variety Protein encoding is only a minor function of RNA ▪ Mechanisms of gene-experience interactions unknown o 5 important discoveries in epigenetics ▪ Nongene DNA = junk DNA is WRONG Cuz these active nongene DNA controls structural gene expression ▪ Epigenetic mechanisms that can modulate gene expression DNA methylation o A reaction that occurs when a methyl group attaches to a DNA molecule (usually Cytosine sites) in mammals Histone remodeling o a reaction that occurs when histones change their shape which will then change the shape of an adjacent DNA ▪ Histones: proteins where DNA is coiled around Both can increase or decrease expression ▪ Worldwide effort to catalogue the epigenome of each cell type Epigenome: represents a catalogue of all the modifications to DNA within a particular cell type other than changes to the nucleotide base sequence ▪ Some epigenetic effects involve post-transcription alterations to RNA that do not affect the RNA base sequence Epigenetic modifications of messenger RNA & transfer RNA High prevalence of these RNA modifications has led to a new effort o Epitranscriptome: all those modifications of RNA that occur after transcription ▪ Does not involve modifications to the RNA base sequence ▪ Epigenetic mechanisms can be induced by experiences Neural activity, hormonal state, changes to the environment ▪ Transgenerational epigenetics: examines the transmission of experiences via epigenetic mechanisms across generations  Like natural selection A subfield of epigenetics Questions o According to Mendel’s experiments, the dominant trait will result in abt three-q uarters of the offsprings in the second generation o An offspring’s observable traits are called its phenotype while its genetic material is referred to as genotype o A single trait is controlled by 2 expressions of the same gene called alleles o Egg & sperm cells are also called gametes, & each contains half the usual number of chromosomes o During fertilization, the resulting zygote contains a full set of chromosomes o The 4 nucleotide bases in DNA are adenine, thymine, cytosine, & guanine o Accidental errors in individual genes are called mutations o Promoters are stretches of DNA that control the process of gene expression o Epigenetic mechanisms such as DNA methylation & histone remodeling may control gene o The shape of DNA can be influenced by the change of shape of the adjacent histone o All chromosomes except sex chromosomes come in matched pairs o The first phase of gene expression involves the transcription of DNA to RNA, and the second phase involves the translation of RNA base- sequence code into a sequence of amino acids o Human Genome Project discovered that only 1% of human DNA contains protein-encoding genes Epigenetics of Behavioral Development: Interaction of Genetic Factors & Experience Discuss what insights into the genetics of behavior were gained from early research on selective breeding Explain how classic research on phenylketonuria (PKU) has informed our understanding of the genetics of behavior ----------------------------------------------------------------------------------------------------------------- Terms to know o Ontogeny: refers to the development of an individual through their lifespan o Phylogeny: refers to the evolutionary development of a species through the ages  o Behavioral development is a consequence of genetic potential interacting with the experience of an individual organism Selective Breeding of Maze-Bright & Maze-Dull Rats o Cooper & Zubek (1958) study of maze-bright & maze-dull rats ▪ Reared maze-bright & maze-dull rats in one of the 2 environments An impoverished environment o A barren wire-mesh group cage An enriched environment o A wire-mesh group cage that contained tunnels, ramps, visual displays, & other objects designed to stimulate interest ▪ When maze-dull rats reached maturity, they made more errors than maze-bright rats ONLY IF they had been reared in the impoverished environment o Tryon (1934) behavioral traits can be selectively bred ▪ Bred fittest maze-bright rats tgt & dullest maze-dull rats tgt for 21 generations By 8 generation, there was almost no overlap in the maze learning performance of the 2 groups of rats ▪ Used cross-fostering control procedure Maze-bright offspring raised by maze-dull parents & maze-dull offsprings raised by maze-bright parents o No changes Phenylketonuria: A Single-Gene Metabolic Disorder o Phenylketonuria (PKU): neurological disorder discovered in 1934 o High levels of phenylpyruvic acid found in urine o Symptoms ▪ Intellectual disability, vomiting, seizures, hyperactivity, irritability, & brain damage o Transmitted by a single gene mutation ▪ PKU develops only in homozygous individuals cuz its a recessive gene (aa) o PKU homozygotes lack phenylalanine hydroxylase ▪ An enzyme required for the conversion of the amino acid phenylalanine to tyrosine ▪ Result: phenylalanine accumulates in the body & levels of dopamine (synthesized from tyrosine) are low  Leads to abnormal brain development o Behavioral symptoms result from an interaction between genetic & environmental factors ▪ High phenylalanine levels, placed on phenylalanine restricted diet Reduces both the amount of phenylalanine in the blood & the development of intellectual disabilities Sensitive period: usually early in life, during which a particular experience must occur to have a major effect on the development of a trait Birdsong Genetics of Human Psychological Differences Explain why it is important to distinguish between the development of individuals & the development of individual differences Explain heritability estimates & how they are commonly misinterpreted Describe 2 ways that twin studies can be used to study the interaction of genes & experience (i.e., nature & nurture)