Editing Dominance (genetics) (section)

===Epistasis===
{{Main|Epistasis}}

Epistasis is interactions between multiple alleles at different loci. More specifically, epistasis is when one gene can mask the phenotype of a gene at a completely different locus.<ref name=":4">{{Cite book |last1=Urry |first1=Lisa A. |title=Campbell Biology |last2=Cain |first2=Michael L. |last3=Wasserman |first3=Steven A. |last4=Minorsky |first4=Peter V. |last5=Orr |first5=Rebecca B. |publisher=Pearson Education, Inc. |year=2021 |isbn=9780135188743 |edition=12th |pages=281–282}}</ref> Therefore, several genes can influence the phenotype expressed. Epistasis is slightly different from dominance in the fact that dominance is an allele-to-allele interaction at one locus while epistasis is a gene-to-gene interaction at different loci.<ref name=":5">{{Cite book |last=Pierce |first=Benjamin A. |title=Genetics: a conceptual approach |date=2024 |publisher=Macmillan Learning |isbn=978-1-319-33778-0 |edition=Seventh edition digital update |location=Austin}}</ref> The dominance relationship between alleles involved in epistatic interactions can influence the observed phenotypic ratios in offspring.<ref>{{Cite journal |last=Phillips |first=Patrick C |date=2008 |title=Epistasis - the essential role of gene interactions in the structure and evolution of genetic systems |journal=Nat Rev Genet |location=London |publisher=London: Nature Publishing Group |volume=9 |issue=11 |pages=855–867 |doi=10.1038/nrg2452 |issn=1471-0056 |pmc=2689140 |pmid=18852697}}</ref>

An example of epistasis can be seen in Labrador retriever coat colors. One gene at one locus codes for the color of hair but another gene at a different locus determines if the color is even deposited in the hair.<ref name=":5" /><ref name=":4" /> Recessive epistasis is seen in this example due to recessive alleles for color desposition masking both the dominant black (B) allele and recessive brown (b) allele at the first locus to express a yellow coat in the Labrador retriever.<ref name=":5" /><ref name=":4" /> The yellow color comes from no pigment being deposited in the hair shaft.<ref name=":5" /> 

Other examples of epistasis interactions are dominant epistasis and duplicate recessive epistasis.<ref name=":5" /> Each type of epistasis is a modification of the dihyrbid ratio of 9:3:3:1.<ref name=":4" />