There are three base alleles' to consider when setting out to create visual mutations (Morphs) - Recessive, Dominant and Co-dominant. In order to put these three alleles' into practice, along with some of the other reptile genetic terminology defined in the previous section, we will create many different breeding scenerios on the following pages to help put a lot of it into perspective.
Here is a three column diagram, which separates a few of the popular Ball Python genetic mutations into their gene's respective alleses. This is by no means a complete list of all of the possible genetic mutations. There are currently over 3,800 different morphs in existence!
Recessive - The recessive alleles can only be passed on to the offspring phenotypically (visually) when both the mother and father carry the same recessive gene. For instance; If both the mother and father do not carry the Albino gene, Albino offspring cannot be produced. The offspring would instead have the appearance of a normal Ball Python, but would be Heterozygous (normal 100% het for Albino). No matter what any given Homozygous recessive alleles gene animal is bred to, the offspring will always be 100% Heterozygous for that gene. For example: If an Axanthic animal was bred to a normal, every offspring produced would visually look normal, but they would be 100% Heterozygous for Axanthic. If two different genes from the recessive alleles are bred together, every one of the offspring will be Double Heterozygous. That is to say, if an Albino was bred to an Axanthic, neither Albino or Axanthic offspring would be produced. All of the offspring will appear visually normal, but they will be Double Heterozygous for Albino and Axanthic. If a recessive alleles gene animal is bred to either a dominant or codominant alleles gene animal, for instance; Breeding a Clown gene animal to a Spider gene animal, 50% of the offsping will be normal Het Clown and 50% will be Spider Het Clown.
Dominant - Unlike the recessive alleles, the mother and father do not both have to carry the same visual gene in order to pass it on to the offspring phenotypically. However, when both parents do carry the same gene it increases the odds. As with the codominant alleles, the visual genes are passed on to the offspring 50% of the time when bred to other genes. For example: If the dominant alleles Spider Ball Python was bred to a normal Ball Python 50% of the offspring would be normal and 50% would be Spiders. "Super" forms cannot be produced in dominant alleles gene animals. For instance: If a Spider was bred to a Spider, 75% of the offspring would be Spiders and 25% would be normal.
Co-dominant - Co-dominant alleles genes work almost the same as the dominant alleles genes. The only difference is, Super forms can be produced in codominant alleles genes, whereas they cannot be produced in the dominant alleles genes. For example: If a Pastel was bred to a Pastel, 25% of the offspring will be Super Pastel, which means when those Super Pastels are bred in the future they will not produce any normals. In other words, no matter what the Super Pastel is bred to in the future, all of it's offspring will at least be Pastel.