The Leatherback is actually a visual het for the scaleless dragon. A dragon that displays this trait is a heterozygous carrier of the trait. This means that the leatherback is heterozygous (het) for scaleless (the complete reduction or absence of scaling). These are our favorite genetics, and we have found it most interesting among the other available bearded dragon mutations.
Leatherbacks popped up randomly in a breeders collection. As we recall, the breeder produced a dragon that showed significant reduction in tubercles. (What are tubercles? Tubercles are the raised scales found on the back and other parts of the bearded dragon)
He used this dragon, and produced more like it through the next generation breeding. When he then crossed the animals displaying this characteristic to each other, he produced an animal with what appeared to be no scales at all (silkback). He consistently produced these results. The founding breeder crossed the originally displaying animals (leatherback) to a red line and a yellow line of bearded dragons. This produced the red and yellow leatherback lines that we have today. These animals were continually crossed to the smoother animals to produce the smoothest quality leatherbacks.
The reason why these animals are so easy to outcross is because you can see a physical characteristic which indicates the animals genetics. This is known as a genetic marker, in this case being the reduction of tubercules. You can see it’s a leatherback, so you know it’s het for the silkback gene. It makes things simpler than your recessive genetics with no visible genetic markers.
Just as the translucent gene, we like to refer to the leatherbacks as low expression leatherbacks and high expression leatherbacks. There are significant varying levels of the smoothness in the leatherback appearance. These include slightly reduced tubercles all the way to leatherbacks that have severe scale and tubercle reduction.
Click on image for a larger view.
Although leatherbacks have been originally bred to produce a reduction in tubercles, some leatherbacks have been bred to show a reduction in the actual size of the scale as well. Say an average scale is a 1/16 square, the leatherbacks have shown to be able to reduce that scaling to lets say 1/32 square. This makes the appearance of the scaling much smaller. A lot of leatherbacks will have a wrinkle like look to them because of this genetic mutation.
Leatherbacks are known for showing significant reduction in tubercles on the back, on the sides of the base of the tail closest to the body. They are also known for the absence of or severe reduction of the scaling in the lateral spines.
When leatherbacks are bred to each other, 25% of their clutch consist of the visual homozygous animals, these animals are scaleless.
Written by http://www.dragonfortress.com/