Allele = One letter (pronounced Al-eel)
An allele is a version of a gene. They are usually represented by one letter. It’s easiest to remember what an allele is by picturing it as one letter.
An eel (allele) can look like a letter.
B = brown eye colour
b = blue eye colour
Each allele is represented in a punnet square.
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.