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Personality and Genetics.docx

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Connie Boudens

Personality and Genetics Cell Biology Basics Cell nucleus contains DNA Carries genetic information Controls growth and development 23 pairs of chromosomes One gene = 46 chromosomes Phenotype vs. genotype Genotype = specific genetic makeup  Non-visible Phenotype = how genetic makeup is expressed  Visible. o Examples: eye colour, height. Forms of Gene Expression Dominant-recessive: one dominates Codominance and incomplete dominance: neither dominant, or one dominant - doesn’t hide effects of other  Codominance: both expressed  Incomplete dominance: combination expressed Polygenic: Many pairs of alleles create expression Role of Environment Phenotype = Genotype + environment +gene-environment interaction +gene-environment correlation Genotype-Environment Interactions Impact of environment depends on genotype  Example: Religious upbringing reduces influence of genetic factors on disinhibition. Genotype-Environment Correlation Differential exposure of individuals with different genotypes to different environments Passive: Parents provide both genes and environment to children.  Child’s verbal ability and the number of books in home Reactive / evocative: Parents (or others) respond to children depending on the genotype  Baby’s liking for cuddling and mother’s cuddling behavior Active: Person with particular genotype seeks out environment  High sensation seekers expose themselves to risky environments Passive decreases with age, active increases Genotype-environment correlations can be positive or negative Behavioural Genetics Attempt to determine % of individual differences in a trait due to genetic and % due to environment Determine the ways genes and environment interact and correlate Determine what relevant environmental factors are. Heritability: amount of individual difference in trait due to genetic differences. Environmentality: extent to which individual differences are due to environmental differences Misconceptions About Heritability Heritability CANNOT be applied to single individual  Only applies to group-level variation ( Heritability NOT constant or immutable  Environment homogenous? - heritability higher  Environmental variations increase - heritability will be lower  Even highly heritable traits modifiable by environment Heritability NOT a precise statistic – think estimate Behavioral Genetics Methods Selective Breeding—Studies of Humans’ Best Friend Can only occur if a desired trait is heritable  Evaluates genetic involvement by attempting to breed for high and low extremes of a trait for several generations. Done using animals ( analogue experiment)  Ex: depressed mice Family Studies Correlates degree of genetic overlap among family members with similarity in trait If trait is highly heritable, those more closely related should be more similar. Problem: Members of a family share elements of the environment—confounds genetic with environmental influences  Thus, family studies never definitive Twin Studies Estimates heritability by seeing if MZ twins are more similar than DZ twins  If true, the MZ twins should be more similar than the DZ twins because they share 100% of the same DNA as opposed to only 50%. This would mean that genetic influences would have more influence than environment, if true. Video:  Clusters of personality traits (Dark Triad – Machiavellianism, narcissism, psychopathy) o This isn’t a diagnosed personality disorder but its edging towards one  The study is trying to establishing that the Triad does group together but also has to be considered separate o Do they make individual differences to personality? o W
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