Complex sentence: Because of the way that the science of population genetics was developed, evolutionary geneticists have tended to think of epistasis as the exception however, in general, the expression of any one allele depends in a complicated way on many other alleles.
Split into simpler sentences: Because of the way that the science of population genetics was developed, evolutionary geneticists have tended to think of epistasis as the exception. However, in general, the expression of any one allele depends in a complicated way on many other alleles.