Multiple Alleles Definition Biology

Explore the concept of multiple alleles in biology and its impact on genetic diversity and traits in organisms. Learn about examples, case studies, and the significance of multiple alleles.

Introduction to Multiple Alleles

In biology, alleles are different versions of the same gene that can result in different traits. While most genes have only two alleles (one from each parent), some genes have multiple alleles, meaning there are more than two variants of that gene within a population. This phenomenon is known as multiple alleles.

Understanding Multiple Alleles

Multiple alleles can exist for a single gene because of the presence of more than two different alleles in a population. Each individual within the population can only have two of these alleles—one from each parent. However, the total number of alleles present in the population can vary, leading to different combinations and outcomes.

Examples of Multiple Alleles

One of the most well-known examples of multiple alleles in humans is the ABO blood group system. This system is determined by three alleles: A, B, and O. Individuals can have any combination of these alleles, resulting in four blood types: A, B, AB, and O. Another example is the gene responsible for coat color in rabbits, which has multiple alleles leading to a variety of coat colors.

Case Studies on Multiple Alleles

A classic case study on multiple alleles is the gene for human eye color. While the genetics of eye color are complex and involve multiple genes, the OCA2 gene is known to have multiple alleles that influence the amount of melanin produced in the iris, resulting in different eye colors such as blue, brown, and green.

Significance of Multiple Alleles

Understanding multiple alleles is important in fields such as genetics, evolutionary biology, and medicine. It helps researchers study genetic diversity within populations, the evolution of traits, and the inheritance of genetic diseases.


Multiple alleles play a crucial role in shaping the genetic diversity and phenotypic traits seen in all living organisms. Studying multiple alleles can provide valuable insights into the inheritance patterns of genes and the variability of traits within populations.

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