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 expected phenotypic ratio in the F₁ generation is A)9:3:3:1. B)100 percent of one phenotype. C)1:1. D)1:2:1. E)none of these.

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A dog homozygous for both dominant traits (erect ears and barking) will have the genotype EE BB. When mated with a droopy-eared, silent follower (ee bb), all offspring (F1 generation) will be heterozygous (Ee Bb) and will express the dominant phenotype (erect ears and barking). Thus, 100 percent of the F1 generation will have the same phenotype.

Some Dogs Have Erect Ears; Others Have Drooping Ears