2. Psychiatric Disorder: Is It All In The Genes?

3. Why might a disorder run in families? §Shared genes §Shared environment §A combination of the two

4. behaviour

5. Natural experiments teasing apart genes and environment Twin studies : is there more similarity monozygotic ( one egg) than dizygotic ( two egg) pairs? Adoption studies: do individuals resemble their biological relatives more than adopting relatives?

6. MZ TWINS §MZ (monozygotic) twins have 100% of their genes in common (they’re ‘natural clones’) §Shared environment also makes them similar

7. DZ TWINS §DZ (dizygotic) twins have 50% shared genes §They also share environment to roughly the same extent as MZ twins

8. MZ and DZ Twin Similarity Expressed as Correlations

9. Types of Gene Environment Interplay §Coaction §Interaction §Covariation §Additive §Multiplicative §G & E correlated

10. Coaction §Phenotype= Genes (G) + Environment (E) Shared Non-shared

11. GE Correlation Vs Interaction §Correlation: genetic influence on exposure to different environments §Interaction: genetic control of sensitivity to different environments

12. Finding genes §One of the major benefits of the Human Genome Project is a dense map of markers (“signposts”for genome searching) §Linkage studies use genetic markers track genes in families §Association studies can pinpoint genes in populations

13. Positional cloning §Linkage(or LD) §location §gene identification §structure and sequence §gene product prediction diagnosis treatment

14. Specific genes that interact with environments § serotonin transporter, social adversity (and medication) => depression §Monoamine oxidase A,childhood maltreatment => antisocial behaviour §COMT, cannabis => schizophrenia

15. The impact of genetics: Post genomic psychiatry §targeted & tailored treatments §refined diagnosis §understanding of neurobiology §risk prediction and gene-environment effects §public perception and stigma