Andalusian Chickens


  • One allele is not completely dominant over another
  • The heterozygous phenotype is a blending of the two homozygous phenotypes
  • Incomplete Dominance is similar to, but not the same as Codominance
  • There is an intermediate phenotype between the two parents, as there is no dominant allele
  • This often causes the heterozygote to have a phenotype that is intermediate to both homozygotes
  • In 1760 a German scientist named Josef Kolreuter an example of incomplete dominance


  • An Andalusian chicken is an example of Incomplete Dominance
  • They came to the UK around 1846 when some birds were imported from Andalusia, Spain
  • They are a rare breed that produces 160-200 large white eggs per year


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