Having the ability to roll or curl the tongue up along both sides to form a tube is a dominant trait. Which diagram represents the chromosomes in a person that does not have this ability?

Let H represent the dominant allele for being able to roll the tongue, and h represent the recessive allele. A person who cannot roll the tongue must have two recessive alleles, hh, because even one H would produce the dominant trait. Choice A shows two chromosomes labeled h.

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