Editing Dominance (genetics) (section)

==Relationship to other genetic concepts==
Dominance can be influenced by various genetic interactions and it is essential to evaluate them when determining phenotypic outcomes. [[Allele|Multiple alleles]], [[epistasis]], [[Pleiotropy|pleiotropic]] genes, and [[Polygene|polygenic]] characteristics are some factors that might influence the phenotypic outcome.<ref name=":3">{{Cite journal |last=Ingelman-Sundberg |first=M. |date=2005 |title=Genetic polymorphisms of cytochrome P450 2D6 (CYP2D6): clinical consequences, evolutionary aspects and functional diversity |journal=Pharmacogenomics J |location=United States |publisher=United States: Nature Publishing Group |volume=5 |issue=1 |pages=6–13 |doi=10.1038/sj.tpj.6500285 |issn=1470-269X |pmid=15492763 |s2cid=10695794}}</ref>

===Multiple alleles===
{{Main|Allele#Multiple alleles}}Although any individual of a diploid organism has at most two different alleles at a given locus, most genes exist in a large number of allelic versions in the population as a whole. This is called [[Polymorphism (biology)|polymorphism]], and is caused by mutations. Polymorphism can have an effect on the dominance relationship and phenotype, which is observed in the [[ABO blood group system]]. The gene responsible for human blood type have three alleles; A, B, and O, and their interactions result in different blood types based on the level of dominance the alleles expresses towards each other.<ref name=":3" /><ref>{{Cite journal |last1=Yamamoto |first1=F |last2=Clausen |first2=H |last3=White |first3=T |last4=Marken |first4=J |last5=Hakomori |first5=S |date=1990 |title=Molecular genetic basis of the histo-blood group ABO system |journal=Nature |volume=345 |issue=6272 |pages=229–233 |bibcode=1990Natur.345..229Y |doi=10.1038/345229a0 |pmid=2333095 |s2cid=4237562}}</ref>

===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" />

=== Pleiotropic genes ===
{{Main|Pleiotropy}}

Pleiotropic [[gene]]s are genes where one single gene affects two or more characteristics. An example of this concept is [[Marfan syndrome|Marfan Syndrome]] which is a mutation of the FBN1 gene. The effects this causes are a person's appearance being tall and long limbed. They can also have Scoliosis, Ectopia Lentis, and larger than normal aortas. <ref>{{Citation |last=Dietz |first=Harry |title=FBN1-Related Marfan Syndrome |date=1993 |work=GeneReviews® |editor-last=Adam |editor-first=Margaret P. |url=http://www.ncbi.nlm.nih.gov/books/NBK1335/ |access-date=2025-04-27 |place=Seattle (WA) |publisher=University of Washington, Seattle |pmid=20301510 |editor2-last=Feldman |editor2-first=Jerry |editor3-last=Mirzaa |editor3-first=Ghayda M. |editor4-last=Pagon |editor4-first=Roberta A.}}</ref> Pleiotropy shares a relationship with [[Epistasis]]. While pleiotropy represents one single gene, epistasis is multiple genes interacting with one another to cause different traits to arise.  it is helpful to recognize how Epistasis could affect viewing pleiotropic genes if different traits arise or mask themselves to varying degrees.<ref>{{Cite journal |last1=Dwivedi |first1=Sangam L. |last2=Heslop-Harrison |first2=Pat |last3=Amas |first3=Junrey |last4=Ortiz |first4=Rodomiro |last5=Edwards |first5=David |date=2024 |title=Epistasis and pleiotropy-induced variation for plant breeding |journal=Plant Biotechnology Journal |language=en |volume=22 |issue=10 |pages=2788–2807 |doi=10.1111/pbi.14405 |issn=1467-7652 |pmc=11536456 |pmid=38875130|bibcode=2024PBioJ..22.2788D }}</ref>

=== Polygenic characteristics ===
{{Main|Polygene}}

Polygenic characteristics are those affected by multiple genes at different loci.<ref name=":6">{{Cite book |last=Pierce |first=Benjamin A. |title=Genetics: A conceptual approach |publisher=Macmillan Learning |year=2024 |edition=7th}}</ref> These different genes interact in a way to produce a [[Quantitative genetics|quantitative characteristic]], which is a characteristic that presents a wide variety phenotypes, such as height in humans.<ref name=":6" /> The greater the number of genes that interact to influence this characteristic, the greater the number of different phenotypes possible due to more possible genotypes.<ref name=":6" /> Many more characteristics also appear to be affected by more than one gene located on different loci, including diabetes and some autoimmune diseases.<ref name=":7">{{Cite journal |last=Boyle |first=Evan |date=2017 |title=An Expanded View of Complex Traits: From Polygenic to Omnigenic |url=https://doi.org/10.1016/j.cell.2017.05.038 |journal=Cell |volume=169 |issue=7 |pages=1177–1186|doi=10.1016/j.cell.2017.05.038 |pmid=28622505 |pmc=5536862 }}</ref>