Comment by StevePrefontain
6 days ago
How do geneticists go about identifying alleles associated with autism? Seems like the effect size would be very small for most of them, and given the relatively small sample population of humans that can be practically sequenced for this, it seems difficult to separate true signal from statistical noise.
Also is it actually just “a sum of cumulative effects of these alleles crossing a threshold causes autism” or more complex like “Allele A and B together has a very significant effect, A and C has a moderate effect but A, B, and C together is has no effect”
What's an allele? There is no real answer to that question. Or rather, the concept of allele is highly abstract and does not correspond well to actual genomic sequences.
Predicting phenotypes is not a linear function of the genome. It's a highly nonlinear function, affected by complex generative processes, feedback control, homeostasis, and many other active control mechanisms. With that said, you could come up with a proxy score that was a function of the genome and had predictive value for autism (ideally better than binary, with a description of the predicted autistic traits somebody showed).
Biology is the only field I've worked in where both "necessary but not sufficient" and "sufficient but not necessary" can both be the case at the same time.