A hybrid is an organism that has two different alleles for a particular trait. The most common way to represent this in genetics is using two different letters.

Here's how it works:

* Alleles: Different versions of the same gene. For example, a gene for flower color might have an allele for red (R) and an allele for white (r).

* Homozygous: An organism with two of the same allele (RR or rr).

* Heterozygous: An organism with two different alleles (Rr). This is the hybrid.

So, to represent the genes of a hybrid, you would use two different letters, such as Rr, where "R" represents one allele and "r" represents the other.