11. However, the findings of epigenetics suggest that this may not be an appropriate way to define epistasis . 12. Strong positive epistasis is sometimes referred to by creationists as irreducible complexity ( although most examples are misidentified ). 13. This leads to negative epistasis whereby mutations that have little effect alone have a large, deleterious effect together. 14. This is indicative that a phenomenon such as multiple alleles or epistasis may have a role in determining morphology. 15. Synergistic epistasis is central to some theories of the purging of mutation load and to the evolution of sexual reproduction. 16. Background genetic effects ( modifier genes ), epistasis , somatic variation, and environmental factors all complicate the situation. 17. Epistasis is the dependence of the effect of one gene or mutation on the presence of another gene or mutation.18. This does not take into account the effects of epistasis , which would probably increase the number of related genes. 19. When deleterious mutations also have a smaller fitness effect on high fitness backgrounds, this is known as " synergistic epistasis ". 20. Selection that influences epistasis is a case where the regulation or expression of one gene, depends on one or several others.
