Behavior genetics studies

Answer: How heredity AND environment contribute to individual differences Twin and adoption studies estimate the relative contributions.

The pattern of concordance rates most directly suggests which inference?

Answer: Genetic factors contribute substantially to the disorder's etiology Higher MZ than DZ concordance indicates a genetic contribution. However, MZ concordance below 1.0 shows environmental factors also matter.

Dizygotic (fraternal) twins share, on average,

Answer: About 50% — the same as any siblings Two separate eggs fertilized by two different sperm.

AP Psychology · Topic 1.1

Interaction of Heredity and Environment Practice

Part of Biological Bases of Behavior.

Practice questions

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Sample questions

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Sample 1difficulty 3/5
$Behavior genetics studies$
- A
  $How heredity AND environment contribute to individual differences$
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- B
  $How genes alone determine personality and intelligence$
- C
  $How identical twins differ from fraternal twins behaviorally$
- D
  $How upbringing alone shapes psychological development$
Why
$Twin and adoption studies estimate the relative contributions.$
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Sample 2difficulty 3/5
$A research team examines concordance rates for a mood disorder across 800 monozygotic and 800 dizygotic twin pairs raised together. They report concordance of 0.55 for monozygotic pairs and 0.22 for dizygotic pairs. The investigators apply behavioral genetic models to estimate heritability while acknowledging shared environment as a covariate.$
$The pattern of concordance rates most directly suggests which inference?$
- A
  $Concordance rates prove a single-gene cause$
- B
  $Environmental factors play no role in the disorder$
- C
  $Genetic factors contribute substantially to the disorder's etiology$
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- D
  $The disorder is fully determined by genetics$
Why
$Higher MZ than DZ concordance indicates a genetic contribution. However, MZ concordance below 1.0 shows environmental factors also matter.$
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Sample 3difficulty 3/5
$Dizygotic (fraternal) twins share, on average,$
- A
  $About 75% — more than full siblings$
- B
  $About 100% — they share identical DNA$
- C
  $About 25% — the same as half-siblings$
- D
  $About 50% — the same as any siblings$
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Why
$Two separate eggs fertilized by two different sperm.$
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Sample 4difficulty 3/5
$Monozygotic (identical) twins share approximately what percentage of DNA?$
- A
  $25%$
- B
  $50%$
- C
  $75%$
- D
  $100%$
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Why
$Develop from a single fertilized egg \to genetically identical.$
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Sample 5difficulty 3/5
$"Heritability values are population estimates, not individual." — adapted from twin literature$
$Based on the chart, which trait shows the LOWEST heritability?$
- A
  $Extraversion$
- B
  $Specific religious affiliation$
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- C
  $Height$
- D
  $IQ$
Why
$Specific religious affiliation is largely determined by family/cultural environment, not genes—it shows the smallest bar. Note: heritability estimates apply to populations, not individuals.$
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