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The same goes for a cause we'd consider purely environmental, such as an illness caused by an infection. There will still be lots of associated genes with small
by unishark 6y ago
The same goes for a cause we'd consider purely environmental, such as an illness caused by an infection. There will still be lots of associated genes with small effect determining how resilient a person is to the infection. Twins share environmental causes from early stages of development (like an infection during pregnancy) so that angle gets potentially confounded too.
- ravi-delia 6y agoTwin studies typically compare identical and fraternal twins to eliminate such environmental factors (Obviously there are still errors, but they generally wind up as counting towards environmental). And of course polygenetic factors probably have a sort of necessary-but-not-sufficient type of relationship with the traits they contribute too, but that doesn't mean that anything that isn't pegged to a single gene can be thought of as environmental.