Heredity & Environment
Lecture 2 - September 11th, 2013
Behaviour Genetic s -
Contributions of heredity and environment.
Differences in human behaviour.
Focus on heritability factors.
Environmental influences play a major role.
Methods of Study: Twin -
Monozygotic (MZ) vs. dizygotic (DZ) twins.
Separated at birth or early in life.
Genotype constant with varying environments.
(a) small sample
(b) lack of control
Methods of Study: Adoption -
Examine two types of relationships:
(a) Adopted child & adoptive parents
(b) Adopted child & biological parents
(a) Lack of data availability
(b) Selective placement
(c) Homogeneity of adoptive homes
Genotype vs. Phenotype -
Set of genes inherited from parents.
Observable & measurably expression.
Examined by psychologists.
Genetic Transmission -
Ovum + Sperm = 23 pairs of chromosomes
Genes & DNA -
Genetic information contained in deoxyribonucleic acid (DNA).
Chemical bases – adenine, thymine, guanine, & cytosine.
Order of bases determine organism and characteristics.
Based on protein production.
Entire DNA sequence.
Blueprint for organisms.
Monomorphic vs. polymorphic genes. Where does variability come from? -
On individual genes.
Meiosis: simple genetic transmission.
Random mixing & crossing over of genetic information.
Homozygous vs. heterozygous.
Sex Chromosomes -
Determine the person's sex.
XX - female
XY - male
Variability: Additive -
Each parent passes an allele, which determines offspring characteristic.
Runs in families.
Variability: Configural -
Emergenesis (Lykken, 1982).
Emergenic traits will not run in families, but identical twins will share them.
Change in one component results in a qualitatively different trait.
Genetic but do not run in families.
MZ correlations greater than twice DZ correlation.
Facial Beauty -
Attractiveness of one facial feature depends on