Lec 2 Part A - Genes, Environment, and Prenatal Development

Flashcards covering key terms and concepts related to genes, environment, and developmental psychology.

Behavioral Genetics

What are the three mechanisms of inheritance?

The study of the effects of genes and environment on behavior.

1. Single gene-pair: trait is influenced by ONE pair of genes e.g. eye color

2. Sex-linked: traits are influenced by genes located on sex chromosomes, typically X-linked. E.g. color blindness

3. Polygenetic: traits are influenced by multiple genes, resulting in a continuous range of phenotypes, such as height.

Heritability (in twin studies, what’s the equation?)

The proportion of variation in a trait in a population attributable to genetic differences, ranging from 0 to 1. (not a stable nor fixed number)

=> In twin studies, Total variance = Genes + Shared environment + Nonshared environment

Note: non-shared factors often explain more variation in adulthood as we age we get into more of these enviro.

Phenotype

The observable characteristics or traits of an organism resulting from the interaction of its genotype with the environment.

Twin Studies

Research comparing the similarity of identical twins to fraternal twins to understand genetic influence.

Core logic: if MZ twins have greater similarity, this suggests some level of genetic influence. Therefore, it can help separate nature and nurture.

Adoption Studies

Research comparing adopted children to their biological and adoptive parents to isolate genetic and environmental influences.

Similarity to biological parents suggest genetic effects

Whereas similarity to adoptive parents suggest environmental effects

Family studies: Core logic

Compare relatives with graded genetic similarity => full siblings (50%), half siblings (25%), step-siblings (0%)

Estimate both genetic and environmental contributions, cost-effective complement to twin and adoption studies

Molecular genetics studies

Link specific gene variants to traits and behaviors

Genome-wide association studies (GWAS) are used to identify risk variants

Estimates around 10% of variance can be explained be genetic influences

Intelligence: heritability key findings

General samples of overall heritability

Age trends

Moderation the effect of SES - is this found cross-culturally?

1. 50%

2. Genetic influences with age as individuals select environments that fit their genes (overall fluctuation)

3. With high SES, there is high heritability (around 72%), but with low SES there is low heritability (around 10%)

Core logic: in an adequate environment (higher SES), we’re more likely to have adequate opportunities e.g. books. This helps our genetic potential to be reached => environmental limitations suppress genetic expression

BUT not all replication studies show similar results, Australia, for example, has a social welfare program, so the SES findings might not apply there

What is the Wilson effect?

• Amplification

• Niche-picking

• Shared environment

Genetic influence on intelligence increases significantly with age

• Genetic differences grow larger over time

• Selecting environments that match genotype

• Declining influence from childhood to adulthood

Temperament and Personality - Heritability

• Genetic contribution

• Nonshared environment

• Shared environment

1. 40% of the variation in major personality dimensions among adults is attributable to genetic differences

2. 55% of unique life experiences account for the majority of personality variance

3. 5% of common family experiences have a minimal effect on adult personality similarity

How much heritability do the Big 5 traits show?

What is the effect of temperament in infancy?

Overall, what dominates personality?

1. 35-45% Stability increases with age, genes exert stronger influence

2. Temperament in infancy predicts adult personality (early biological programming - longitudinal studies) but life experiences e.g. accidents can shape personality throughout lifespan

3. Nonshared environment: unique life experiences create significant personality differences between siblings, e.g. peer groups, differential parental treatment or expectations, social niches.

Psychological conditions/disorders overview

• What type of genetic liability and environmental tr_ggers

• Does heritability vary widely by condition?

• Is family history deterministic?

• What is crucial for onset and course?

1. Polygenetic liability

2. Yes, by 20-80%

3. No, it only increases risk

4. Environmental factors

Case study: Schizophrenia

• Heritability

• Twin studies MZ vs DZ twins

• Adoption studies

• 80%, one of the highest heritability rates among psychological disorders

• 48% for MZ twins vs 17% DZ twins (3x more likely for MZ twins)

• Increased risk if a biological parent is affected, regardless of adoptive home environment

Other examples:

• Depression

• ADHD

• Autism spectrum

1. 40%, which stress trriggers

2. 75%, neurodevelopmental

=> pharmological and behavioral support available

3. 80%, neurodevelopmental (early identification can be useful_

Neurodevelopmental: in early development, something in the brain is already altered

Note: environmental support improves outcomes for many conditions

What is gene-environment interactions?

Genetic effects depend on environment context

Same gene variant can confer risk OR resilience depending on environment quality

High quality environments may compensate for potential genetic vulnerabilities

GxE

Diathesis-Stress Model

A model that explains how genetic predisposition and environmental stressors interact to produce mental disorders.

Diathesis - vulnerability, we all carry hidden genetic risk

Stress - the trigger, environmental stressor

Their interaction is the key => diathesis and stress together leading to an outcome

GxE

Differential susceptibility

Some individuals are more malleable to environmental quality

• Some are highly sensitive to BOTH negative and positive environments

• Some are more resilient and less affected by environmental variation

GxE

Study: Caspi et al. (2003)

• Core finding

• Alleles

• Replication studies

1. Genetic vulnerability is conditional on environmental exposure

2. Short allele is the genetic vulnerability; under high stress, short-allele carriers had significantly higher rates of depression after childhood maltreatment. Under supportive environments/low stress, short allele carriers showed minimal or no increased risk (in comparison to long-allele carriers)

3. Genes create latent risk and environment affects the expression. Replication attempts have shown mixed results

Genetic Amplification

The phenomenon where genetic influence on traits becomes stronger as individuals grow older.

rGE (GxE correlations)

Passive Gene-Environment Correlations

Evocative Gene-Environment Correlations

Active (niche-picking) Gene-Environment Correlations

1. Situation where parents provide genes and environments that match those genes.

   1. Athletic parents passing athletic genes and creating a sports-oriented family culture (reinforces genetic predispositions => ice-hockey Hughes family)

2. When a person’s genetically influenced traits (personality) elicit specific responses from others in their environment.

   1. A sociable infant receives more social engagement, is likeable and treated more positively

3. The process where individuals actively search for environments that suit their genetic predispositions.

   1. Early childhood

   2. Middle childhood (growing choice - select activities and friends)

   3. Adolescence (active seeking - compatible enviro. beyond home)

   4. Adulthood (niche - niches fitting genetic predispositions)

Epigenetics

• DNA methylation

• Histone modification

The study of changes in gene expression caused by environmental factors other than changes in the underlying DNA sequence.

=> diet, stress, toxins, social experiences

1. Silence DNA sequence by adding a small chemical tag

2. Can loosen or tighten genes

What are some implications and ethical issues in genetics?