White & Yellow Leopard Geckos
A White & Yellow leopard gecko carries a stark white and yellow base with faded, broken markings and a reduced pattern. Breeders cross it into other lines, Snow crosses especially, to brighten and clean them up, much as they use Enigma.
About the White & Yellow gene
The White & Yellow morph gives a leopard gecko a base of stark white and yellow with markings that are faded and broken. Because of how it looks on its own and how it works when crossed into other lines, breeders want this one.
Appearance
Striping runs down the back of an adult White & Yellow, which has high white sides and bright, high-contrast colour over a reduced, faded pattern. A large white band across the nape often breaks the irregular pattern on the head. These animals usually hatch with very little carrot tailing and tails that are mostly white. From animal to animal, colour balance varies. Some lean more yellow, others more white, and orange appears occasionally.
Genetics
White & Yellow is a line-bred trait instead of a single-locus gene. The record on Morphpedia, which quotes breeder Ron Tremper, calls the effect Polygenetic Dominance. Because the trait appears in roughly half of a generation's offspring, the hobby often treats it as a dominant gene. It is called polygenic rather than dominant by breeders who work it in volume, including Jeff Galewood of JMG Reptiles after he produced more than forty. A homozygous form is sold as Super White & Yellow, but test breeding has never confirmed if that animal looks any different from a single-copy White & Yellow. The two are not the same gene even though they look similar as adults, as a separate test-breeding project by Matt Baronak found that White & Yellow does not carry the Enigma gene's eye traits and has not shown Enigma's stargazing or spinning. Prohorchik Reptiles first produced it in 1996. To brighten and clean up other lines, especially Snow crosses, breeders use it the way they use Enigma. Combinations with names include Aurora (with Bell Albino) and Universe (with Super Snow and Eclipse).
Known issues
A mild balance problem has appeared in some White & Yellow lines where the geckos overstep slightly while walking. This has not been confirmed to come from the White & Yellow gene itself and does not appear in every line. It can be reduced within a generation or two through outcrossing and careful pair selection according to breeders who have run into it.