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Personality and Genetics.docx

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Department
Psychology
Course
PSYB30H3
Professor
Connie Boudens
Semester
Summer

Description
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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