• The interaction of genes that are not alleles, in particular the suppression of a gene by a different gene.
  • E.g. windows peak:
    • Allele results in a “V shaped” hair
    • Another allele expressed results in baldness
    • Therefore, if carrier of both, as the person is bald the allele for widow’s peak is unclear

Phenotypic ratios for Epistatic Genes

  • Recessive Epistatic Alleles
    • If the epistatic allele is recessive then 2 copies of it will mask the expression of the other gene
    • Homozygous parent + homozygous parent = 9:3:4 phenotypic ratio

(dominant both: dominant epistatic/recessive: recessive epistatic (in F­2))

  • Dominant Epistatic Alleles
    • If the epistatic allele is dominant then 1 copies of it will mask the expression of the other gene
    • Homozygous parent + homozygous parent = 12:3:1 phenotypic ratio

(dominant epistatic: recessive epistatic, dominant other: recessive (in F­2))