TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Pages 94-107 Consider the merits or otherwise of an argument or concept. Opinions and conclusions should be presented clearly and supported with appropriate evidence and sound argument Study needed!!

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Genotype and Phenotype All cells in the human body that have a nucleus contain a set of CHROMOSOMES A thread-like structure that contains a DNA molecule Humans have 23 pairs of chromosomes (46 total) One from mom, one from dad. Both chromosomes in the pair have a code for identical characteristics, but the chromosomes themselves might not be identical DNA stores info. It is a code made up of a long sequence of four chemical bases. The bases are paired up, making a sequence of base pairs. Double helix: looks like a twisted ladder Human DNA consists of about 3 billion bases A gene is a unit of heredity, a region of DNA that encodes a specific trait or function. Estimated 20,000 genes in a human organism Alleles are different forms of a gene They can be dominant or recessive The set of traits as coded in an individual’s DNA is called genotype. The set of traits that actually manifest in an individuals body, appearance or behavior is called phenotype.

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Nature vs. Nurture debate Today, it is widely recognized that the debate needs to be reformulated There is little doubt that human behavior is influenced by both genetics & brain structure (nature) and environmental factors (nurture) What is more interesting is to answer the following questions? What are the relative contributions of biological and environmental factors into a specific behavior? Ex. How important is biology or environment in developing intelligence? How do biological and environmental influences interact?

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Methods of research Twin studies Comparing similarities between monozygotic (identical) twins and dizygotic (fraternal) twins. If identical twins are more similar than fraternal twins, we can attribute it to genetic influences Family studies: Uses the principle of genetic relatedness: comparing children to parents, grandparents, siblings, cousins, etc. Adoption studies: Compare adopted children to their adoptive parents, biological parents, adoptive siblings, and biological siblings. Molecular genetics: based on using modern technology for genetic mapping and identifying the alleles of particular genes in a particular individual. Genetic variants are then correlated with observed behavior.

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? We cannot study genes directly and how they combine with other genes and the environment Scientist rely on statistical models using correlations to analyze data about the behavioral effects of genes Statistical relationships, not “cause and effect”

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Genetic heritability: the Falconer model Genetic heritability is the quantitative measure of the relative contribution of genetic factors into a trait or behavior. The Falconer model assumes that phenotype comprises three types of influences: genetics (A), shared environment (C), and individual environment (E), 1 = A + C + E Genetic heritability (A) can be estimated by directly measuring the similarity (correlation) between monozygotic (rMZ) and dizygotic twins (rDZ) Shared environment is the part of environmental influences that is common to the two twins (similar schooling, same exposure to technology, etc.) Individual environment comprises environmental influences that are unique to each of the twins (different friends, different hobbies, etc.)

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Heritability of intelligence: twin studies Bouchard and McGue (1981) Conducted a meta-analysis of 111 studies on IQ correlations between relatives Aim: on page 100 Methods: on page 100 Results: on page 100 Limitations: on page 101

TO WHAT EXTENT DOES GENETIC INHERITANCE INFLUENCE BEHAVIOR? Heritability of intelligence: adoption studies IQ scores tend to be more similar for child-biological parent than for child-adoptive parent IQ scores tend to rise when child is adopted into more prosperous families This is called the additive influence of genetics and environment on the development of intelligence Scarr and Weinberg – “Minnesota Adoption Studies” (1983) Aim: on page 102 Methods: on page 102-103 Results: on page 103