Allele is the variant forms of a gene with one of two or more forms in a single gene. Each person inherits two alleles for each gene, one from each parent.
Since alleles are the variant forms of a gene, these variations are the reason we are all different from each other.
Alleles have a variety of different forms, which are located at the same position on a chromosome. These differences in variations, named SNP’s, control an individual’s speed of metabolism and reactions to medications.