Three or more forms of a gene that code for a single trait are called what?

• A. Alleles
• B. Multiple alleles
• C. Codominance
• D. Polyploidy

Answer: (B)

When a gene has more than two variants in a population, those variants are called multiple alleles. A gene can come in different versions, and if there are three or more versions present in the population, we describe them as multiple alleles. Individuals still carry only two alleles for that gene (one from each parent), but the population’s diversity of alleles creates more potential phenotypes. For example, the gene that determines blood type has several alleles, leading to multiple possible blood types. Codominance describes a situation where both alleles are expressed in the phenotype without one being recessive, which is about how alleles are expressed rather than how many different alleles exist. Polyploidy means having more than two complete sets of chromosomes, which is about chromosome number, not the number of alleles for a single gene.