Gene birth contributes to structural disorder encoded by overlapping genes

S. Willis; J. Masel

Overlapping genes are particularly evolutionarily constrained because a mutation in an overlapping region simultaneously affects both of the two (or occasionally more) genes involved in that overlap. Because ∼70% of mutations that occur in the third codon position are synonymous, versus only ∼5% and 0% of mutations in the first and second codon positions respectively [38] , a mutation that is synonymous in one reading frame is highly likely to be nonsynonymous in another, so to permit adaptation, overlapping genes must be relatively tolerant of nonsynonymous changes. Demonstrating the higher constraint on overlapping regions, they have lower genetic diversity and d N /d S than non-overlapping regions in RNA viruses [25] , [39] , [40] , [43] .