Which type of allele is expressed regardless of the second allele?

The correct choice describes a dominant allele, which is expressed phenotypically regardless of the identity of the second allele present in the genotype. In genetic terms, an individual has two alleles for each gene—one inherited from each parent. When at least one dominant allele is present in the genotype, its trait or characteristic manifests in the organism's phenotype.

For instance, if we consider a gene that influences flower color where a dominant allele (let's say "R" for red) is present alongside a recessive allele (let's say "r" for white), the presence of the "R" allele will ensure that the flower is red, even if the second allele is "r". Thus, the dominant allele effectively overrides the effect of the recessive one in determining the observable characteristic.

In contrast, recessive alleles only express their traits in the absence of a dominant allele (e.g., only when both alleles are recessive). Homozygous refers to having two identical alleles (either both dominant or both recessive) for a gene, and heterozygous means having one of each type (one dominant and one recessive). Neither homozygous nor heterozygous terms describe the expression of an allele; they refer