I am SO glad that SOMEBODY put this thread on the right track!!
If anybody wants a full explanation of this trait and its inheritance, I suggest looking up VPI's website, and a few of the other really big, professional breeders' websites.
It's really amazing how many people are involved with breeding Ball Pythons and don't know squat about genetics!! What's worse is that those who are already misinformed then spread their "understanding" of the topic, and post their explanations on a website - and if it looks good, then obviously the information must be good too.
Biochemically speaking, an organism must be able to produce Tyrosinase in order to be able to produce melanin (pigment responsible for black and brown coloration), because Tyrosinase is a chemical that must be slightly modified in order to create melanin. Melanin cannot exist without Tyrosinase first.
The reason that Caramel Albinos have some brown to them has to do with their ability to produce Tyrosinase, and by bioprocesses we don't need to go into here, small amounts of that Tyrosinase are turned into melanin, but the animal is not able to make melanin in significant amounts on its own, as the animals that we consider to be normal can. The mutation affects the animal's ability to transform all of its Tyrosinase into melanin.
This is why the white-and-yellow albinos and lavender-and-yellow albinos are referred to as "T [minus] albino" (or lacking the ability to produce Tyrosinase), while the Caramels are called "T [plus] albino" (as they apparently can produce Tyrosinase, but still lack enough melanin that they are classified as albinos).
Thanks for reading my rantings.
~Rebecca
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1.1 Ball Pythons (1.0 '05 Ghost, 0.1 '03 Normal)
0.1 Dumeril's Boa '04
0.2 American Pit Bull Terriers (40 lb darling lap dogs)