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Chapter 4

Chapter 4 Notes

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Psychology 1000

Chapter 4: Genes, Evolution, and Behaviour Chapter Outline Genetic Influences Chromosomes and Genes Behaviour Genetics Techniques Applications Genetic Counselling Genetic Influences on Behaviour Heredity, Environment, and Intelligence Focus on Neuroscience The Neuroscience and Genetics of Dyslexia Biological Reaction Range, the Environment, Personality, and Intelligence Evolution and Behaviour Evolution of Adaptive Mechanisms An Evolutionary Snapshot of Human Nature Evolutionary Psychology Research Foundations Gender Differences in the Ideal Mate How Not To Think About Behaviour Genetics and Evolutionary Psychology Frontiers Inequality, Competition, and Murder Genetic Influences Chromosomes and Genes Genotype: the specific genetic makeup of an individual. Genotypes are present from birth and never change. Phenotype: the observable characteristics produced by that genetic endowment. Phenotypes can be affected by other genes and the environment. Chromosome: is a tightly coiled molecule of deoxyribonucleic acid (DNA) that is partly covered by protein. Genes: segments of DNA that contain instructions to make proteins-the building blocks of life. Each chromosome contains numerous genes. • Every cell in the body has 46 chromosomes. • Exception: sex cell has 23 chromosomes. o 23 chrosms from the egg + 23 chrosms from sperm=zygote (46 chrosms) o 2 copies of each gene cells Alleles: alternative forms of a gene that produces different characteristics. Genes affect our body’s development and functioning through one general mechanism: Code for the production of proteins: • Control the structure of individual cells and all chemical reactions that go within those cells • Target brain structure and function • Each individual gene carries the code for a specific protein Dominant, Recessive, and Polygenic Effects • Dominant: the particular characteristic that the gene controls will be displayed • Recessive: the characteristic will not show up unless the partner gene inherited from the other parent is also recessive. • Polygenic Transmission: A number of gene pairs combine their influences to create a single phenotypic trait. Genetic Engineering: The Edge of Creation Recombinant DNA procedures: researchers use certain enzymes to cut the long threadlike molecules of genetic DNA into pieces, combine them with DNA from another organism, and insert them into a host organism, such as a bacterium. Inside the host, the new DNA combination continues to divide and produce many copies. Gene knockout: alter a specific gene in a way that prevents it from carrying out its normal function (used to observe behaviour) Behaviour Genetics Techniques Heritability coefficient: The extent to which variation in a particular characteristic within a group can be attributed to genetic factors is estimated statistically by heritability coefficient. Heredity vs. Heritability Heredity: means the passage of characteristics from parents to offspring by way of genes. Heritability: means how much of the variation in a characteristic within a population can be attributed to genetic differences (e.g. Notice a range of body weights. The heritability coefficient is a way of estimating how much of that variation is attributable to genetic factors) Concordance: the likelihood that two people share the same characteristic Adoption study: a person who was adopted early in life is compared on some characteristic both with the biological parents, with whom the person shares genetic endowment, and with the adoptive parents, with whom no genes are shared. *If the adopted person is more similar to the biological parents then a genetic influence is suggested. If greater similarity is shown with the adoptive parents, then environmental factors are more important. Twin studies: A behaviour genetics method in which identical and fraternal twins are compared on some characteristic; this method is particularly informative if the twins have been raised in different environments. Genetic and environmental factors almost always interact with each other to influence behaviour. Genetic Influences on Behaviour Heredity, Environment, and Intelligence • Genes play a significant role in intelligence • IQ of identical twins raised together is higher than identical twins raised apart • Same is true for other types of siblings raised together and apart • Genes only account for 50 to 70% of the IQ variation • Environment contributed significantly to intelligence Focus on Neuroscience The Neuroscience and Genetics of Dyslexia Dyslexia: difficulty learning to read • Familial transmission (heritable) • Genetic factors are very important in the development of dyslexia • Genetic contribution to the entire range of reading ability, not only dyslexia • Spelling and phonological coding (influenced by genetics) • Affects brain development • Differences in the left temporal lobe affect reading ability Biological Reaction Range, the Environment, Personality, and Intelligence Reaction range: the range of possibilities – the upper and lower limits – that the genetic code allows. An individual inherits a range for potential. Environmental effects will determine where the person falls within these genetically determined boundaries. Potential is jointly influenced by 2 factors: • Genetic inheritance • Opportunities our environment provides *Different combination of genes underlie specific abilities Behaviour Genetics and Personality • Specific personality traits can be traced to differences in brain development or function Five Factor Model (differences in personality can be accounted for by variation along 5 broad personality dimensions: 1. Extraversion-Introversion (outgoing vs. quiet) 2. Agreeableness (cooperative vs. uncooperativeness) 3. Conscientiousness (responsible vs. undependable) 4. Neuroticism (worrying vs. well-adjusted) 5. Openness to experience (imaginative vs. unreflective) 40-50% of the personality variation among people is attributable to genotype differences. *Genetic factors accounted for 39 to 58% of the variation among people in personality trait scores (the degree of resemblance did not differ much whether the twins were reared together or apart) *Unique experiences, and individual learning experiences accounted for 36 to 56% of the variation in individual personality traits Attitudes toward preservation of life, equality, and athleticism had the highest genetic component. • Direct relationship between genes and attitude is unlikely: Certain inherited factors (muscle coordination) may predispose individuals to prefer certain activities. Evolution and Behaviour Evolutionary psychology seeks to understand how behavioural abilities and tendencies have evolved over the course of time in response to environmental demands. Biologically based mechanisms: mechanisms that receive input from the environment, process the information, and respond to it. No behaviour such as aggression, altruism, sex roles, protecting kin, and mate selection ever evolves. What evolves is genetically produced physical structures that interact with the demands of the environment to produce behaviour. Evolution of Adaptive Mechanisms Evolution Evolution: Is a change over time in the frequency with which particular genes-and the characteristics they produce-occur within an interbreeding population. Mutations: random events and accidents in gene reproduction during the division of cells. If mutation occurs in reproductive cells, the mutation is passed on the offspring. Natural Selection Natural selection: characteristics that increase the lik
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