In a strict dominant-recessive system, which allele determines the phenotype when present?

In a strict dominant-recessive system, which allele determines the phenotype when present?

• A. Recessive allele
• B. Neither
• C. Dominant allele
• D. Allele order

Answer: (C)

In complete dominance, the phenotype follows the presence of the dominant allele. If at least one copy of the dominant allele is present, that trait is expressed, masking the recessive allele even when the genotype is heterozygous. Only when both alleles are recessive does the recessive phenotype appear. The recessive allele matters for genotype but does not determine the phenotype when a dominant allele is present. The idea of any “order” of alleles doesn’t influence the outcome. So the allele that determines the phenotype when present is the dominant allele.

In complete dominance, the phenotype follows the presence of the dominant allele. If at least one copy of the dominant allele is present, that trait is expressed, masking the recessive allele even when the genotype is heterozygous. Only when both alleles are recessive does the recessive phenotype appear. The recessive allele matters for genotype but does not determine the phenotype when a dominant allele is present. The idea of any “order” of alleles doesn’t influence the outcome. So the allele that determines the phenotype when present is the dominant allele.