Ohhhkay.

Because I was curious, I had to look up what causes the piebald spotting in piebald mice. Apparently, it has been known for a long time to be due to a deficiency in neural crest cell derived melanocytes. (The "neural crest" is a group of cells that migrate along the embryo and produce lots of different cell types in the body.)

Recently, it was discovered that the exact cause of the deficiency is a mutation in a signal molecule that "turns on" the melanocytes. Without that signal molecule, most of the melanocytes don't turn on and therefore the animal has white patches in those areas. According to these researchers, the amount of white is directly correlated to the level of expression of the signal molecule. Animals with almost no signal molecule are all white (and also have other diseases), while animals with 25% normal functioning signal molecule are about 20% white.

However, in the mouse model, the amount of signal molecule was determined by different alleles -- in mice, there are apparently multiple different piebald alleles on the same locus. I don't think that can possibly be the case with piebald ball pythons since if it were, the amount of white would presumably have a very clear inherited component. Also, even normal piebalds have a pattern that is really distinct from normal ball pythons, which is kind of interesting and suggests to me that there may be more to it than "just" an ablation or lack of activation of melanocytes ...

Here's an article, for those interested (I'm not enough of a molecular geneticist to want to go all that crazy with most of it, but the abstract and discussion have some interesting points about the mechanism):

http://www.jbc.org/content/281/16/10799.full.pdf

This isn't the article in which they describe the original finding, but it's interesting nonetheless and I can't post that article in its entirety without violating copyright

As far as the heritability factor, I thought I had heard tell of a few folks working with lines of extreme low-white pieds. Is this not the case after all?