Psychology 5137

1
Psychology 5-137

• Topic 14
• Conclusion

2
Definition

• Behavioral genetics - that area of psychology
  that is concerned with the application of genetic
  methods and research designs to study the nature
  and origins of individual differences in human
  and animal behavior.

3
Methodologies

• Mendelian (single-gene) inheritance
• PKU, Huntingtons, CAH
• Chromosomal anomalies
• Down Syndrome, Williams Syndrome, VCFS
• Twin/Adoption Studies
• Complementary methodologies
• Biometric Analysis
• Variance component estimation
• Gene Identification in Humans
• Linkage, Association, Linkage Disequilibrium
• Animal Methods
• Selection, Inbred Strains, Forward Genetics (QTL,
  mutagenesis, microarray), Reverse Genetics
  (transgenics, knock-outs)

4
Nature of Genetic Influence

• Heritability
• Virtually all behavioral traits are in part
  heritable
• Common heritable factors may account for
  correlations among disorders (Krueger et al.,
  2002)
• Heritability estimates are approximations
• Heritability is not an index of immutability
  behavior is genetically influenced not
  genetically determined (ALDH and culture)

5

• A 70 percent heritability estimate is pretty
  wild, said Dr. Norman Krasnegor, chief of the
  Human Learning and Behavior Branch of the
  National Institute of Child Health and Human
  Development. He said that if it was true, it
  shouldn't matter too much what you do or where
  you go to school. Everything would fall into
  place.''
• NY Time, 12 October 1990

6
Nature of Genetic Influence

• Genes and the Human Genome Project
• 30,000 genes and 11,000,000 SNPs in the human
  genome
• Mendelian vs. oligogenic vs. polygenic
• Gene identification for complex phenotypes has
  been difficult
• Structural vs. regulatory
• Gene identification for complex phenotypes
  (positional cloning strategy) has been difficult
• Alternative Strategies
• Large-scale LD studies (500,000 SNPs) in humans
• Homology synteny in other species

7
Nature of Environmental Influence

• Familial resemblance is potentially a function of
  both shared genes and shared environment
• Have we overestimated the impact of parents?
• Shared vs. non-shared environmental effects
• Changing balance across development for some
  traits
• SZ, BP, Depression, ADHD
• Gene-environment interplay
• GxE and the diathesis-stress model
• PKU
• MAO-A and aggression
• 5HTTLPR and depression
• G-E correlation
• Ge et al. adoption study

8
Principled Critiques of BG

• For psychologists, as well as for medical
  researchers, the purpose of identifying
  undesirable predispositions of individuals should
  be to devise more effective health-promoting
  interventions, not to discourage such attempts on
  the supposition that these predispositions are
  genetically based and therefore intractable.
  
• D. Baumrind (1993)

9
Final Admonitions

• Dont believe it unless it is replicable
• Single studies are not definitive, require a
  coherent pattern of results
• Study for the final attend review session on
  Thursday 12 May from 300 - 430 in N227 Elliott
  Hall
• Arrive for the final on time (1330, Saturday May
  12 in N391)