What distinguishes dominant traits from recessive traits?

The distinguishing factor between dominant and recessive traits is primarily based on the requirement of alleles for expression. Dominant traits require only a single copy of the dominant allele to manifest in the phenotype, meaning that if an individual inherits one dominant allele from either parent, that trait will be expressed. In contrast, recessive traits necessitate two copies of the recessive allele for the trait to be expressed. This means that for a recessive trait to appear, an individual must inherit the recessive allele from both parents.

This misunderstanding often leads to confusion, as individuals might think that dominant traits are "better" than recessive ones, but this is not the case; they simply have a different mode of inheritance. The other options are less accurate regarding the principles of genetics. Dominance does not equate to benefit, as traits can be neutral or harmful regardless of their dominance. The relative frequency of traits in the population doesn't determine their classification as dominant or recessive, and dominant traits cannot be masked by other dominant traits; they only get masked by recessive alleles. Thus, understanding the fundamental roles of alleles in trait expression clarifies the distinction between dominant and recessive traits.