3.4.2 Twin and Adoption Studies

• What do twin studies compare to estimate the genetic contribution to a trait?

  Monozygotic vs Dizygotic twins
• Adoption studies examine the similarity between adopted children and their biological versus adoptive parents
• Twin studies are used to estimate the genetic contribution to a trait by comparing monozygotic and dizygotic twins.
• Adoption studies help separate genetic and environmental influences by comparing adopted children with their biological and adoptive parents.
• What percentage of genes do monozygotic twins share?

  Nearly 100%
• Dizygotic twins share approximately 50% of their genes
• Match the type of twin with its characteristic:

  Monozygotic Twins ↔️ Identical, share ~100% genes

  Dizygotic Twins ↔️ Fraternal, share ~50% genes
• High concordance rates in monozygotic twins compared to dizygotic twins suggest a strong genetic influence.
• Dizygotic twins arise from two separate eggs fertilized by two different sperm
• Monozygotic twins share approximately 100% of their genes.
• What does a higher concordance rate in monozygotic twins compared to dizygotic twins suggest about genetic influence?

  Strong genetic influence
• Steps in conducting twin studies

  1️⃣ Identify twin pairs (MZ and DZ).

  2️⃣ Assess and compare trait(s) of interest.

  3️⃣ Calculate concordance rates for each twin type.

  4️⃣ Compare concordance rates between MZ and DZ twins.
• High concordance in MZ twins versus DZ twins suggests a strong genetic influence
• Adoption studies separate genetic and environmental influences by comparing adopted children with their biological and adoptive parents.
• Match the study type with its purpose:

  Twin Studies ↔️ Estimate genetic contribution

  Adoption Studies ↔️ Separate genetic & environmental influences
• What is the primary purpose of twin and adoption studies in biological psychology?

  Differentiate genetic and environmental factors
• Steps in conducting adoption studies

  1️⃣ Recruit participants (adopted children and parents).

  2️⃣ Assess traits in each group.

  3️⃣ Compare similarities between children and both parent groups.

  4️⃣ Analyze data to determine genetic or environmental influence.
• Twin studies analyze concordance rates to determine genetic influence.
• Monozygotic twins arise from a single fertilized egg
• Match the type of twin with its genetic similarity:

  Monozygotic Twins ↔️ ~100%

  Dizygotic Twins ↔️ ~50%
• Comparing concordance rates between monozygotic and dizygotic twins helps infer genetic influence.
• What is the primary goal of adoption studies in biological psychology?

  Genetic vs environmental influence
• Adoption studies compare traits between adopted children and their biological and adoptive parents
• Steps in conducting adoption studies

  1️⃣ Recruit participants

  2️⃣ Assess traits

  3️⃣ Compare similarities

  4️⃣ Analyze data
• Adoption studies measure traits only in adopted children and their biological parents.

  False
• Match the study type with its primary goal:

  Twin Studies ↔️ Estimate genetic contribution

  Adoption Studies ↔️ Separate genetic and environmental influences
• What is the first step in an adoption study?

  Recruit participants
• If adopted children resemble their biological parents in intelligence scores, it suggests a strong genetic influence
• Twin and adoption studies are only used to understand behavioral traits.

  False
• What does comparing monozygotic (MZ) and dizygotic (DZ) twins in twin studies help control for?

  Environmental factors
• Adoption studies separate genetic and environmental influences by comparing adopted children to their biological and adoptive parents
• Twin and adoption studies can completely eliminate environmental influences.

  False
• What is the Equal Environments Assumption in twin studies?

  MZ and DZ twins share similar environments
• Selective placement in adoption studies can affect results because adopted children may be placed in environments similar to their biological parents
• Twin studies estimate heritability by comparing concordance rates between MZ and DZ twins.
• What is the primary purpose of twin and adoption studies in biological psychology?

  Differentiate genetic and environmental factors
• What is the primary purpose of twin studies and adoption studies in biological psychology?

  Separate genetic and environmental factors
• If monozygotic twins have higher concordance rates for a disorder than dizygotic twins, genes likely play a significant role.
• Monozygotic twins share nearly 100% of their genes.
• Dizygotic twins share approximately 50% of their genes, similar to ordinary siblings.