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Epistasis and Complementation definitions

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  • Complementation Test
    A cross used to determine if two mutants with the same phenotype have mutations in the same or different genes.
  • Epistasis
    A gene interaction where one gene masks or alters the expression of another gene, changing expected phenotypic ratios.
  • Nonepistatic Genes
    Genes affecting the same phenotype independently, resulting in a classic 9:3:3:1 Mendelian ratio.
  • Dominant Epistasis
    A dominant allele at one gene masks the effect of another gene, producing a 12:3:1 phenotypic ratio.
  • Recessive Epistasis
    A recessive allele at one gene masks the effect of another gene, leading to a 9:3:4 phenotypic ratio.
  • Complementary Gene Action
    Two genes in the same pathway both require a dominant allele to produce a phenotype, typically yielding a 9:7 ratio.
  • Suppressor Gene
    A mutant allele that reverses the effect of a mutation in another gene, often restoring the wild type phenotype.
  • Modifier
    A gene that alters the degree of expression or severity of a mutated gene's phenotype.
  • Synthetic Lethal
    A situation where two viable single mutations cause lethality when combined, affecting phenotypic ratios.
  • Phenotypic Ratio
    The proportion of different observable traits among offspring, often altered by gene interactions.
  • Genotypic Ratio
    The proportion of different genetic combinations among offspring, typically 9:3:3:1 in dihybrid crosses.
  • Wild Type
    The most common or standard phenotype observed in a population, often restored by complementation or suppressors.
  • Mutant
    An organism or allele with an altered genetic sequence, often resulting in a non-standard phenotype.
  • Masking
    The phenomenon where one gene's allele prevents the expression of another gene's phenotype.
  • Pathway
    A series of gene products or proteins that interact to produce a specific phenotype, as seen in complementary gene action.