Identifying Epistasis

• What is epistasis?

  One gene affects the expression of another
• How does epistasis affect phenotypes?

  It alters the expected phenotypic ratios
• What does the combination of alleles dictate?

  The phenotype of an individual
• What are the alleles for the gene dictating pigeon feather color?

  • Allele R: codes for grey feathers
  • Allele r: results in white feathers
• What are the alleles for the gene affecting feather color in pigeons?

  • Allele F: produces an enzyme stopping grey feathers
  • Allele f: does not produce an enzyme
• What phenotype do RRFF pigeons have?

  White feathers
• What phenotype do RRy pigeons have?

  Grey feathers
• What are the possible phenotypes of pigeons with epistasis?

  • 6 phenotypes with white feathers
  • 3 phenotypes with grey feathers
• What phenotypic ratio is expected without epistasis?

  6 grey feathers : 3 white feathers
• What phenotypic ratio is expected with epistasis?

  2 grey feathers : 7 white feathers
• How can unexpected phenotypic ratios help in genetics?

  They can indicate the presence of epistasis
• What is the significance of phenotypic ratios in genetics?

  • Help identify linkage between genes
  • Indicate potential epistasis