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Gene
Usage in Metaphors
The word 'gene' can metaphorically describe non-biological traits, like behaviors or preferences assumed to be inherited. 
Not Always Visible
'Gene' can refer to traits that are not always obvious; some genes can be 'silent' or not expressed. 
Cultural Relevance
In discussions about nature vs. nurture, 'gene' often represents the 'nature' aspect of the debate. 