Which term describes a gene variant that is expressed when present?

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

Answer: (B)

In genetics, the trait that appears in the organism’s phenotype even if only one copy of the allele is present is described as being dominant. So the gene variant that is expressed when present is the dominant allele, because it determines the trait in a heterozygous pair as well as in a homozygous pair. The other terms don’t describe this concept: heredity is the general passing of traits from parents to offspring, biodiversity is the variety of life in an environment, and invasive species are non-native organisms that spread and cause impact.