What is an example of a trait controlled by multiple alleles?

Blood type is an example of a trait controlled by multiple alleles. In humans, the ABO blood group system demonstrates that there are three different alleles: A, B, and O. Each individual inherits one allele from each parent, leading to four possible blood types: A (which can be AA or AO), B (which can be BB or BO), AB (which is a result of one A and one B allele), and O (which is only possible with two O alleles).

This genetic system showcases how multiple alleles can contribute to the phenotypic diversity of a single trait. Unlike traits determined by a simple dominant-recessive interaction, traits influenced by multiple alleles, such as blood type, can produce a wider variety of phenotypes in the population.