3: Developmental 2

Revision questions were posed regarding research designs discussed in the last lecture.
- Cross-Sectional Design: Different age groups with independent participants.
  - Cohort Effect: Potential issue where a variable other than age may affect results due to different participants in each age group.

Transitioned to discussing the interaction of genes and environment in development.
Current understanding: Nature and nurture are not mutually exclusive; both interact and contribute to developmental changes.
Goals for the lecture included:
- Understanding heritability (genetic influence on traits).
- Exploring examples of gene and environment interactions.

Genes: Basic units of heredity containing instructions for protein production.
Chromosomes: Structures containing genes, typically in pairs (23 pairs in most cells)
- Exception: Sperm and egg cells contain 23 individual chromosomes.
Zygote: Fertilized egg formed from the union of sperm and egg.
Genotype vs. Phenotype:
- Genotype: Complete genetic makeup.
- Phenotype: Observable traits influenced by genotype and environment.
Alleles: Variants of a gene; can be homozygous (same) or heterozygous (different).
- Dominant vs. Recessive Alleles: Dominant alleles are expressed over recessive ones.

Subfield exploring interactions of genetic and environmental factors in explaining individual differences.
Heritability: Refers to the proportion of variance in a trait attributable to genetic differences—only meaningful at the group level.
- Expressed as a number between 0 (not heritable) and 1 (completely heritable).
Degree of Relatedness: Probability of gene sharing among relatives, pivotal in studies using twins.
- Monozygotic Twins: Share 100% genes, higher similarity on traits.
- Dizygotic Twins: Share about 50%, like any other siblings.

Twin studies allow researchers to estimate heritability:
- If monozygotic twins show greater similarity in traits compared to dizygotic twins, there is likely a genetic component to that trait.
Examples of heritable traits include:
- Height: Approximately 80% heritability.
- Schizophrenia: About 50% heritable, illustrating environmental influences.
- Intelligence: Estimates range from 50% to 80% heritable, with age-related variance in the influence of genes.

Example 1: MAO A Gene and Conduct Disorder
- Conduct Disorder: Characterized by aggressiveness; childhood maltreatment serves as an environmental risk.
- Findings showed that individuals with low MAO A activity and a maltreatment history were at the highest risk for developing antisocial behaviors.
Example 2: FADS2 Gene and IQ
- FADS2 gene impacts fatty acid metabolism, crucial for brain myelination and development.
- Results indicated that only those with the C allele of the FADS2 gene benefited from breastfeeding in terms of enhanced IQ.

Both genetic components and environmental influences shape developmental traits.
The idea of nature and nurture interacting is crucial in understanding psychological attributes and disorders.
Psych traits, while heritable, require an understanding of their environmental contexts.