Because they are recessive they won't show in the het form. They are only visual when two copies of the recessive gene exist in the same animal. Being het can influence the overall look, such as making them appear a little brighter, or in the case of het for Pied, adding the train track markings. Regardless, the animal will still look very much like whatever the base genes are. For example the picture below is a clutch of double het animals for both Pied and Hypo. The pairing was a Hypo Pied male to a Vanilla female. As you can see everything just looks like Normal or Vanilla. The recessive genes are there but since there is only one copy of each recessive gene present in every snake, nothing visual is displayed. I wouldn't normally breed siblings together, but if I did, I should get some animals that display one or both of the visual forms of the recessive genes. The second picture is the male and what could come from pairing the siblings.
I hope that helps.
Reply With Quote