MCAT Psychological Social Foundations Flashcards: 7a Behavioral Genetics Gene Environment

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This deck focuses on 7a Behavioral Genetics Gene Environment, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Psychological Social Foundations.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the nonshared environment effect ($e^2$) in twin/adoption studies?

Answer: Environmental influences that make siblings different (plus measurement error). Unique experiences and random developmental variation.

Flashcard 2: What is behavioral genetics?

Answer: Study of genetic and environmental contributions to behavior. Examines how genes and environment shape behavioral traits.

Flashcard 3: What is heritability ($h^2$) in behavioral genetics?

Answer: Proportion of phenotypic variance due to genetic variance in a population. Measures genetic contribution to trait variation in a population.

Flashcard 4: State the formula for broad-sense heritability using variances.

Answer: $h^2=\frac{V_G}{V_P}$. Genetic variance divided by total phenotypic variance.

Flashcard 5: What does it mean if a trait has $h^2=0$?

Answer: Genetic variance does not explain phenotypic variance in that population. All trait variation is due to environmental factors.

Flashcard 6: What is the key limitation of heritability estimates across different environments?

Answer: They are environment- and population-specific; they do not generalize universally. Heritability changes with different environments and populations.

Flashcard 7: Identify the definition of polygenic inheritance.

Answer: Multiple genes contribute additively to one trait. Many genes each contribute small effects to one trait.

Flashcard 8: Identify the definition of pleiotropy.

Answer: One gene influences multiple phenotypic traits. Single gene affects multiple seemingly unrelated traits.

Flashcard 9: What is epigenetics in the context of behavior?

Answer: Environment-related changes in gene expression without DNA sequence change. Environmental factors alter gene activity patterns.

Flashcard 10: What is active gene–environment correlation (niche picking)?

Answer: An individual seeks environments consistent with genetic predispositions. People select environments matching their genetic tendencies.

Flashcard 11: What is evocative (reactive) gene–environment correlation?

Answer: An individual’s heritable traits evoke specific responses from others. Genetically outgoing children receive more social interaction.

Flashcard 12: What is the equal environments assumption in twin studies?

Answer: MZ and DZ twins experience equally similar environments relevant to the trait. Assumes environmental similarity is same for MZ and DZ twins.

Flashcard 13: Which twin type is expected to show higher concordance for highly heritable traits: MZ or DZ?

Answer: Monozygotic (MZ) twins. MZ twins share 100% of DNA vs DZ twins' 50%.

Flashcard 14: What is concordance in twin studies?

Answer: Probability that both twins show a trait given that one twin shows it. Measures trait similarity between twin pairs.

Flashcard 15: What is the shared environment effect ($c^2$) in twin/adoption studies?

Answer: Environmental influences that make siblings more similar. Family environment, parenting, and shared experiences.

Flashcard 16: Identify the correct interpretation of heritability: individual or population level?

Answer: Population level; it does not measure an individual’s genetic determination. Describes variance in a population, not individual genetics.

Flashcard 17: What does it mean if a trait has $h^2=1$?

Answer: All phenotypic variance is explained by genetic variance in that population. All trait variation is due to genetic factors.

Flashcard 18: What is passive gene–environment correlation?

Answer: Parents provide both genes and environment correlated with those genes. Musical parents give musical genes and musical home environment.

Flashcard 19: What is a gene–environment correlation (rGE)?

Answer: Genetic differences influence exposure to particular environments. Genes affect which environments individuals experience.

Flashcard 20: What is a gene–environment interaction ($G\times E$)?

Answer: Genetic effects on a trait depend on the environment (and vice versa). Same genotype produces different phenotypes in different environments.

Flashcard 21: What is the key limitation of heritability estimates regarding individuals?

Answer: Heritability does not apply to individuals; it applies to populations. Describes variance in groups, not individual trait causation.

Flashcard 22: What does it mean if $h^2=0$ for a trait in a given population and environment?

Answer: Observed variation is not explained by genetic variation. All trait differences come from environmental factors.

Flashcard 23: State the formula for broad-sense heritability using variance components.

Answer: $h^2=\frac{V_G}{V_P}$. Genetic variance divided by total phenotypic variance.

Flashcard 24: What is heritability ($h^2$) as used in behavioral genetics?

Answer: Proportion of phenotypic variance due to genetic variance in a population. Measures how much genes contribute to trait differences in a group.

Flashcard 25: What is a gene–environment correlation ($rGE$) in behavioral genetics?

Answer: Genetic tendencies influence exposure to particular environments. Genes affect which environments individuals experience.

Flashcard 26: What is the difference between genotype and phenotype?

Answer: Genotype is genetic makeup; phenotype is expressed trait. Genotype is DNA code; phenotype is observable characteristics.

Flashcard 27: What is the main purpose of adoption studies in behavioral genetics?

Answer: Separate genetic effects from rearing (shared) environmental effects. Compares adopted children to biological vs. adoptive parents.

Flashcard 28: Identify the genetic relatedness of dizygotic (DZ) twins.

Answer: Approximately $50\%$ of segregating genes shared. Fraternal twins develop from two zygotes, like regular siblings.

Flashcard 29: Identify the genetic relatedness of monozygotic (MZ) twins.

Answer: Approximately $100\%$ of segregating genes shared. Identical twins develop from one zygote, sharing all genes.

Flashcard 30: What is the twin study logic for estimating genetic influence on a trait?

Answer: Greater MZ than DZ similarity suggests genetic contribution. MZ twins share more genes, so higher similarity implies genetic influence.