<P> Epistasis ( `` epi + stasis = to sit on top '' ) is an interaction between alleles at two different gene loci that affect a single trait , which may sometimes resemble a dominance interaction between two different alleles at the same locus . Epistasis modifies the characteristic 9 : 3 : 3 : 1 ratio expected for two non-epistatic genes . For two loci , 14 classes of epistatic interactions are recognized . As an example of recessive epistasis , one gene locus may determine whether a flower pigment is yellow ( AA or Aa ) or green ( aa ) , while another locus determines whether the pigment is produced ( BB or Bb ) or not ( bb ) . In a bb plant , the flowers will be white , irrespective of the genotype of the other locus as AA , Aa , or aa . The bb combination is not dominant to the A allele : rather , the B gene shows recessive epistasis to the A gene , because the B locus when homozygous for the recessive allele ( bb ) suppresses phenotypic expression of the A locus . In a cross between two AaBb plants , this produces a characteristic 9 : 3 : 4 ratio , in this case of yellow : green : white flowers . </P>
<P> Epistasis ( `` epi + stasis = to sit on top '' ) is an interaction between alleles at two different gene loci that affect a single trait , which may sometimes resemble a dominance interaction between two different alleles at the same locus . Epistasis modifies the characteristic 9 : 3 : 3 : 1 ratio expected for two non-epistatic genes . For two loci , 14 classes of epistatic interactions are recognized . As an example of recessive epistasis , one gene locus may determine whether a flower pigment is yellow ( AA or Aa ) or green ( aa ) , while another locus determines whether the pigment is produced ( BB or Bb ) or not ( bb ) . In a bb plant , the flowers will be white , irrespective of the genotype of the other locus as AA , Aa , or aa . The bb combination is not dominant to the A allele : rather , the B gene shows recessive epistasis to the A gene , because the B locus when homozygous for the recessive allele ( bb ) suppresses phenotypic expression of the A locus . In a cross between two AaBb plants , this produces a characteristic 9 : 3 : 4 ratio , in this case of yellow : green : white flowers . </P>
what type of genetics relationship produces traits utilizing 3 or more genes
what type of genetics relationship produces traits utilizing 3 or more genes
Epistasis
Epistasis