What is used to represent the genes of an organism it’s genotype.
Eg.
If I don’t have freckles then my gene/allele would be Ff or FF because people don’t usually have freckles.
If I had freckles I would be ff because that is a recessive allele.
Also remember that:
GENOtype deals with the genes/alleles
PHENOtype deals with the physical looks of something
An allele and a gene is the same thing