An allele that requires only one gene copy to be expressed is called what?

An allele that requires only one gene copy to be expressed is referred to as dominant. This means that for a trait governed by a dominant allele, the presence of just one copy is sufficient for the trait to be exhibited in the organism’s phenotype. When an individual has at least one dominant allele, it will mask the expression of any recessive alleles present.

In terms of genetics, dominant alleles are represented with a capital letter, and their presence can dictate the expression of traits regardless of the other allele paired with it. For instance, if an organism has one dominant allele for a particular trait and one recessive allele, the dominant trait will be expressed.

The other terms provided relate to genetic concepts but do not accurately describe the allele in question. Recessive alleles require two copies to be expressed, while homozygous refers to having two identical alleles for a gene, which can be either dominant or recessive. Monomer is not a term used to describe alleles, but rather refers to a single unit of a larger molecule, such as nucleotides in DNA. Thus, the defining characteristics of dominant alleles make them crucial in understanding inheritance patterns in genetics.