How does an allele determine a genotype?

1 Answer

An allele is a different form of the same gene.


Alleles are often represented by upper and lower case letters. The upper case letters represent the dominant form while the lower case letters represent the recessive form.

The combination of alleles for any genetic make-up is known as an organism's genotype. There can be many different forms of genotypes, including

AA - Homozygous Dominant
Aa - Heterozygous
aa - Homozygous Recessive

The expression of a genotype is called the phenotype. Otherwise known as the physical traits of an organism.