The phenotype of a living thing is its appearance, meaning how it looks in physical traits. The dominant allele, (the capital letter) means that even when paired with a recessive allele, (the lowercase letter) the phenotype will represent the dominant trait. This means that the plant with the genotype RrTt has a phenotype of red leaves, and tall stems. Bonus: An allele that consists of a dominant gene, and a recessive gene of the same trait, is called a heterozygous allele.
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