What term refers to an allele that is expressed whenever present in an individual?

• A. Heredity
• B. Dominant allele
• C. Invasive species
• D. Succession

Answer: (B)

An allele that is expressed whenever present is a dominant allele. In genetics, dominance describes how alleles influence the phenotype. If an individual has at least one copy of a dominant allele, that trait appears in the phenotype, even if the other allele is different. Only when there is no dominant allele—two recessive alleles—does the recessive trait show. This is why a heterozygous individual (one dominant, one recessive) displays the dominant trait. By contrast, heredity refers to passing traits to offspring, while invasive species and succession are ecological terms unrelated to how alleles are expressed.