A trait controlled by three or more alleles is said to have multiple alleles. This means that there are more than two possible versions of the gene that controls that trait.

Here are some key points about multiple alleles:

* Each individual still only inherits two alleles: Even though there might be many versions of a gene, a single organism will only have two copies of that gene, one from each parent.

* Dominance relationships can be complex: The alleles might exhibit simple dominance, co-dominance, or incomplete dominance.

* Increased phenotypic variation: Multiple alleles increase the number of possible genotypes and phenotypes, leading to greater diversity within a population.

Example:

A classic example is human blood type, which is controlled by the ABO gene. There are three alleles:

* Iᴬ: Codes for the A antigen.

* Iᴮ: Codes for the B antigen.

* i: Codes for no antigen (O blood type).

This leads to six possible genotypes and four possible phenotypes:

* Genotypes: IᴬIᴬ, Iᴬi, IᴮIᴮ, Iᴮi, IᴬIᴮ, ii

* Phenotypes: A, B, AB, O

Important Note: While the term "multiple alleles" often refers to three or more alleles, technically it can apply to any number greater than two.