PPE3003 Exam 3 Genetics and Heritability Genome all of our genes o Around 20 000 genes in our genome o Hierarchy in the genome Genome Chromosomes Genes DNA Behavioral Genetics to what degree are individual differences due to genetic and environmental factors o Controversies Eugenics the social movement claiming to improve the genetic features of human populations through selective breeding and sterilization based on the idea that it is possible to distinguish between superior and inferior elements of society can t select ideal human Genetic determinism have to behave in a certain way genes and Three major questions asked by behavioral geneticists environment interact What causes variability in a trait genes vs environment Which environmental factors are important e g parents teachers peers Heritability how much an individual difference is explained by genetics How do genes and environment interact o Misconceptions CANNOT be applied to single people Example a single individual s height is not 10 due to their environment It is more accurate to say that the variation between people in height is 10 due to environment It is NOT constant unchangeable Heritability only applies to a population at one point in time The more similar the environment between people the higher heritability will be It is NOT a precise statistic 1 PPE3003 Exam 3 Only as good as the sample used e g you should sample people from certain areas Four methods of Behavioral Genetics 1 Selective breeding o Advantages Disadvantages Can t be done ethically with humans Only works if a desired trait is heritable ex Labrador poodle labradoodle If selective breeding for a trait is successful the trait is at least somewhat genetic 2 Family studies o Advantages Disadvantages Correlates genetic similarity with personality similarity If trait is heritable more genetic relatedness more similarity on traits 3 Twin studies 4 Adoption studies Twin Studies o Monozygotic twins Share a single fertilized egg a single zygote monozygotic Share 100 of their genes o Dizygotic twins Come from two separately fertilized eggs two zygotes dizygotic Share about 50 of their genes o Monozygotic correlation dizygotic correlation x 2 Computing heritability Adoption Studies o Correlations on traits between adopted children and adoptive parents environmental influence o Correlations between adopted children and genetic parents genetic o Monozygotic twins are MUCH more similar to each other than dizygotic influence twins o But adopted children aren t tremendously more similar to their biological siblings than their adopted siblings Nonadditive genetic variance the configural or interactive influence of genes on traits Nonadditive genetic variance has been invoked to explain why the ratio of trait concordance for monozygotic twins and dizygotic twins is sometimes greater than 2 0 as in the case of recent studies on extraversion 2 PPE3003 Exam 3 Heritability of o Extraversion 40 60 heritable o Neuroticism 30 54 heritable o Drinking 36 56 heritable o Acloholism 50 71 heritable Any variance not accounted for by genetics is accounted for by environment if height is 90 heritable it is 10 environmental Shared vs Nonshared environmental influence o Shared environment siblings share Environmental influences that operate to make family members alike Twin and adoption studies suggest that shared environments have very little effect on most personality traits o Nonshared environment siblings do not share Environmental influences that operate to make family members different from each other Larger influence on personality Environment genetic interaction people with different genes show different behaviors in the same environment o Ex Extraverts may perform better on a test than introverts if both have studied in a loud public environment Genotype environment correlations o Three types Passive parents provide both genes and environment yet children do nothing to obtain that environment Ex Parents verbal ability of books in house genes child s verbal ability Reactive evocative parents responses differ depending on child Ex Genes baby responds positively to being held baby is held more Active people with particular genotypes seek out particular genotype environments Sensation seeking motorcycle stunts drugs skydiving o Genotype environment correlations can be positive or negative Positive environment facilitates the genetically influenced behavior Negative environment impedes the genetically influenced behavior Molecular genetics aim to identify specific genes associated with personality traits o DRD4 gene codes for dopamine receptor Long repeat version of DRD4 increase in novelty seeking 3 Hypothesized relationship people with long DRD4 genes are relatively unresponsive to dopamine Still inconclusive only explains about 4 of variance PPE3003 Exam 3 Most heritable Big Five traits o Extraversion o Neuroticism o Openness Emergenesis an emergent property of a configuration INTERACTION of genes Some personality characteristics may be a product of emergenesis whereby a unique combination of genes produces an effect that would not be produced in even an attenuated form by the parts that make up the configuration Differences between first borns and younger siblings o Oldest children are likely to identify strongly with the parents and to adopt the traditional viewpoints of authority writ large o By contrast later borns must define themselves over and against the dominant first borns so that they can carve out a niche that will bring them parental resources o Consequently later borns are more likely to adopt a rebellious and contrarian attitude toward authority Six kinds of non shared family effects 1 Perinatal trauma injuries or damage sustained by the fetus before birth Trauma of this sort differentiate the child from all other family members from the beginning 2 Accidental events run the gamut from physical injuries to winning the raffle prize at the state fair Chance happenings and lucky breaks may have an impact on personality serving to differentiate a child further from other family members 3 Family constellation includes birth order and birth spacing between siblings 4 Sibling mutual interaction children in a family interact with one another in complex ways over time forming alliances of various sorts competing and cooperating adopting a wide range of social roles Ex the third daughter in a family of five children may develop an especially close relationship with the
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