| Genetic Interactions |
Article Index for Genetic |
Information AboutGenetic Interactions |
| CATEGORIES ABOUT EPISTASIS | |
| classical genetics | |
| SHOPPER'S DELIGHT | |
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Epistasis and genetic interaction refer to the same phenomenon; however, epistasis is widely used in Population Genetics and refers especially to the Statistical properties of the phenomenon. Studying genetic interactions can reveal gene function, the nature of the mutations, functional redundancy, and protein interactions. Because protein complexes are responsible for most biological functions, genetic interactions are a powerful tool. CLASSIFICATION BY FITNESS OR TRAIT VALUE ]] Two-locus epistatic interactions can be either synergistic (positive) or antagonistic (negative). In the example of a Haploid organism with genotypes (at two Loci ) ''AB'', ''Ab'', ''aB'' and ''ab'', we can think of the following trait values where higher values suggest greater expression of the characteristic (the exact values are simply given as examples): Hence, we can classify thus: Understanding whether the majority of genetic interactions are synergistic or antagonistic will help solve such problems as the Evolution Of Sex . FUNCTIONAL OR MECHANISTIC CLASSIFICATION
EXAMPLE IN MENDELIAN TERMS In a more detailed example, consider the sweet pea plant. In a simple representation, purple flower color (P) is dominant over white (p). However, consider the addition of a control gene, consisting of two Alleles , dominant (C) or recessive (c). In this example, for the flowers to be purple, the plant must have at least one of each dominant allele (i.e. it must be P-C-, where the "-" can be either dominant or recessive). In a Dihybrid Cross , such as the pea plant example above, when there is a genetic interaction involved, you often see a modified 9:3:3:1 ratio. Normally, when you have two alleles which assort independently, you get a 9:3:3:1 ratio of phenotypes. Genetic interactions, however, can conceal the ratio, and make it appear to be something other. In the example of the pea plants above, the result is a 9:7 ratio of purple to white phenotypes instead of the expected 12:4 ratio. SEE ALSO |