Heterozygous (het) Explained

If an animal is said to be Het for a genetic disorder, that means he or she carries the gene required to produce said disorder in their offspring, this is how you can get trans, hypo, and a number of other morph animals from animals that do not visibly display the trait.

You will also see breeders saying that the animal they are selling is X percent het, this is to inform the buyer of the possibility of the gene in the animal, for example a 50% het for trans and hypo animal has a 50% chance to carry both genes. the % het animals are produced by pairing 2 animals that do not display the gene, you can see this in detail on the chart on the hypo page for that particular gene.