allele – a different version of a gene

(Pronounced al-eel)

Note: Alleles are represented by a single letter.

To remember the meaning of allele, use the following mnemonic:

Each letter of the alphabet was formed by an eel (allele) to create a single letter by the genie (gene).

An allele is a variant form of a gene that controls a particular characteristic in an organism. Each gene can have two or more different alleles, and these different versions produce different traits.

Example

B = brown eye colour

b = blue eye colour

Each allele is represented in a punnet square.

NOTE:

In the example below the mother has brown eyes but carries one brown eye allele and one blue eye allele. The father is also brown eyed but again carries one brown eye allele and one blue eye allele.

Each letter represents an allele. One allele is inherited from the father and one from the mother.

The combination of alleles an organism has is called its genotype, while the characteristics that are actually visible are called the phenotype. Understanding alleles is important because they explain how traits are inherited and why offspring can have different characteristics from their parents.