Chap 6: Genetics and Personality

Question 1

Human Genome def.

Answer 1

The complete set of genes that an organism possesses

Question 2

of genes on # of pairs of chromosomes

Answer 2

The human genome contains:

• 20,000-30,000 genes on…
• 23 pairs of chromosomes

Question 3

Similarities in genes in human genome

Answer 3

• most genes in human genome are the same for all humans
• small # of genes are different for different individuals, including genes that indirectly code for physical traits and for personality traits

Question 4

Controversy about genes and personality

Answer 4

• Determine the degree to which individual differences in personality are caused by genetic and environmental differences
• Highly controversial:
  1. Ideological concerns (political agendas-crimes)
  2. Concerns about renewed interest in eugenics
• Finding that a personality trait has a genetic component does not mean that the environment is powerless to modify it

Question 5

Three Goals of Behavioral Genetics

Answer 5

1. Determine the % of individual differences in a trait that can be attributed to genetic differences and % environmental differences
2. Determine the ways in which genes and the environment interact and correlate to produce individual differences
3. Determine precisely where in the “environment” environmental effects exist

Question 6

Two Definitions of Heritability

Answer 6

1. Proportion of observed variance in a group that can be explained by genetic variance
2. Proportion of phenotypic variance that is attributable to genetic variance

Question 7

Phenotypic Variance def

Answer 7

Difference in observable characteristics

Question 8

Environmentality

Answer 8

Proportion of observed variance in a group of individuals attributable to environmental variance

Question 9

Three Misconceptions of Heritability

Answer 9

1. Heritability CANNOT be applied to a single individual
2. Heritability IS NOT constant or immutable
3. Heritability IS NOT a precise statistic

Question 10

Nature-Nurture Debate Clarified

Answer 10

No debate at individual level, environmental influence is only relevant at group-level

Question 11

Four Behavioral Genetics Methods

Answer 11

1. Selective Breeding
2. Family Studies
3. Twin Studies
4. Adoption Studies

Question 12

Selective Breeding

Answer 12

• Can only occur if a desired trait is heritable
• Not ethically conducted on humans
• Dogs example

Question 13

Family Studies

Answer 13

• Correlates the degree of genetic overlap among family members with the degree of similarity in a personality trait
• Problem: members of a family who share the same genes also usually share the same environment
• So, family studies are never definitive

Question 14

Twin Studies

Answer 14

• Estimates heritability by gauging whether identical twins (monotygotic/100% same genes) are more similar that fraternal twins (dizygotic/50% same genes)
• Two assumptions:
  1. equal environments assumption
  2. representativeness assumption
• if MZ more similar than DZ this provides evidence of hereditary

Question 15

Adoption Studies

Answer 15

• • correlation between adopted children and adoptive parents = environmental influence
• • correlation between adopted children and genetic parents = genetic influence
• powerful because it gets around equal environments assumption

Question 16

Attitudes and Preferences

Answer 16

• Wide variance in heritability of attitudes

- Genes appear to influence occupation (on a broad field spectrum)

Question 17

Genetic Influence on Risk of Divorce

Answer 17

• Divorce was significantly higher in MZ twins than DZ twins

- This indicates a strong influence of genetic factors in the etiology of divorce

Question 18

Shared vs nonshared environmental influences

Answer 18

• two key types of environmental influences:
  1. shared: features of the (family) environment shared by siblings (# of books in home)
  2. nonshared: features of the (family) environment that differ across siblings (friends, teachers, activities)
• for most personality traits, the shared environment has little impact
• parents have no effect on personality

Question 19

Genes and the environment: two issues

Answer 19

1. genotype-environment interaction

2. genotype-environment correlation

Question 20

Genes and the environment:

genotype-environment interaction

Answer 20

• Differential RESPONSE of individuals with different genotypes to the SAME environment
• example: task performance of introverts vs extroverts in noisy vs quiet conditions

Question 21

Genes and the environment:

genotype-environment correlation

Answer 21

• Differential EXPOSURE of individuals with different genotypes to DIFFERENT environments
• Three types:
  1. Passive: parents provide genes and environment but children do nothing to obtain that environment
  2. Reactive: parents respond to children differently depending on a child’s genotype
  3. Active: person with particular genotype seeks out a particular environment

Question 22

Molecular Genetics

Answer 22

• Techniques designed to identify specific genes associated with personality traits
• D4DR - gene located on short arm of chromosome 11 associated with novelty seeking