All of the F₁ offspring of Mendel's classic pea cross always looked like one of the two parental varieties because (D) One allele was dominant.
According to law of dominance, traits are regulated by discrete units called 'factors' or genes. These factors occur in pairs (alleles) and in a dissimilar pair of factors, one of the members of this pair dominates the other one.
The one which dominates is known as the dominant allele while the one which remains unexpressed is termed as recessive allele.
The law of dominance is used to explain the expression of only one of the parental traits in a monohybrid cross in the F₁ offspring.
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