Refrigerator mothers and beyond

1. Refrigerator mothers and beyond The aetiology of autism Genetics

2. Genetics of autism • Large number of chromosome abnormalities associated with autism, familial clustering of autism is well above the normal population prevalence, twin-based studies • Hereditability around 90% (Schizophrenia and major depression around 40-50% • Not simple genetic transmission Autisms rather than autism • Evidence from twin studies suggest an MZ to DZ concordance rate of 60% • The rate amongst siblings of an autistic proband is ~3%

3. Genome: 6 billion bits of information from father and mother. We have 99% similarity with only 1% difference • Only a small section codes for genes, the other ‘dark matter’ relating to how genes are expressed into proteins • Suggested that there may be up to 1,000 genes involved in autism. Genes act in an additive way (synergistic) along with the environment to produce the final phenotype

4. Evolution • Twin studies have suggested that autism has high heritability. This occurs in the context of environmental risks and gene-environment interplay. • Autistic traits could have been subject to positive selection pressure, because the benefits of a solitary single-minded obsessive focus • Such individuals might have successfully traded products or their building and fixing skills. Thus acquiring resources and increasing their reproductive fitness, which could have maintained autism alleles in the gene pool

5. Studying the genetics of autism • ‘Guided missiles’ represent experiments where there is a clear hypothesis about the role of a particular region of the chromosome or specific candidate genes • ‘Carpet bombs’ represent studies whereby the whole genome is looked at all at once, looking for genes/chromosomal regions that are associated with ASD. These are ‘genome-wide’ linkage or association studie

6. Examples

7. How might genetic variation occur?

8. Families

9. Theme: Neural development

10. Theme: Social behaviour

11. Theme: Exposure to testosterone