Some dogs have erect ears; others have drooping ears. Some dogs bark when following a scent; others are silent. Erect ears and barking are due to dominant alleles located on different chromosomes. A dog homozygous for both dominant traits is mated to a droopy-eared, silent follower. The phenotypic ratio expected in the F ₁ is A) 9:3:3:1. B) 100 percent of one phenotype. C) 1:1. D) 1:2:1. E) 3:1.

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The F1 generation will all be heterozygous for both traits, showing the dominant phenotype (erect ears and barking) because they inherit one dominant allele for each trait from the homozygous dominant parent.

Some Dogs Have Erect Ears; Others Have Drooping Ears