Complete Dominance: If two alleles have a complete dominance relationship, the phenotype of the heterozygote will be indistinguishable from the phenotype of the homozygous dominant. For example, for one of the gerbil fur color genes, that wild type agouti/brown allele (B) is completely dominant to the black (b) allele of the same gene. BB gerbils are brown; bb gerbils are black; Bb gerbils are brown. And you can't tell by looking at a brown gerbil whether it is BB or Bb, no matter how closely or carefully you look.

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