Charles Pritzel has written 2 editions of an excellent book covering cornsnake genetics and morphs titled the
Cornsnake Morph Guide . It is available for purchase from Cedar Creek Corns. You can use this link to their website:
http://www.cccorns.com/ I don't intend to get as technical as the book, but instead will just try to explain the basics. With the basics understood, using Serp's book for the details won't totally turn your brains into mush. The progeny predictors will also perhaps make more sense.
Now let's start.
When talking about any of the multiple cornsnake morphs, it is always "compared" to what is considered the normal, or "wild-type" cornsnake. All of the genetic morphs are recessive to the dominant normal/wild-type gene. Genes are the blueprint for what the snake will look like. They work in pairs. An individual gets one gene from it's mother and one from it's father. As a very broad example, the sex of humans is determined by the X and Y chromosomes. A woman is XX and a man is XY. The mother can only give an X to her offspring...she is "homozygous" or "homo" X. The father can give either an X or a Y...he is "heterozygous" or "het" Y. The principle is generally the same when discussing homo and het cornsnake genes. Homozygous means there are 2 of the same gene present. Heterozygous means that the 2 genes in the pair are different.
The normal/wild-type genes are dominant over the recessive morph genes. Genes, for use in the Punnett square, are labeled as a letter of the alphabet. Normal/wild-type/dominant genes use the capital letter. The "corresponding" recessive gene(s) that occupies the same place as that dominant gene is written with the lower-case version of the letter. For example:
In the normal corn, the gene pair that says to produce black pigment is AA. The recessive gene pair that says NOT to produce black pigment (to make the snake an amelanistic) is aa. If a normal (AA) is bred to an amel (aa), each snake can only pass on their version to the offspring. Those offspring would be written as Aa. Since the normal gene is dominant over the recessive gene, and the snake possesses one gene to produce black, the snake will be normal in appearance (phenotype) but will be normal het amel in genotype.
The same thing would happen when any or all the recessive corn genes are used. For example:
aa - says don't make black - produces an amel
bb - says don't make red - produces an anery
hh - says reduce the amount of black - produces a ghost
cc - says to change alot of red to yellow - produces a caramel
dd - says to create the diffuse pattern - produces diffuse/bloodred
mm - says to create the motley pattern - produces a motley
ss - says to create the stripe pattern - produces a stripe
ll - says to create the lavender appearance - produces a lavender
Etc.
And you can use whatever letter you want for these morphs as well as all the other recessive morphs.
All of the genes, in either the dominant or recessive form, are found in each and every cornsnake. However, not all may be used when writing a genotype for an individual, only those that will potentially affect the appearance away from the normal or may be passed to offspring.
For example: a hypolavender motley would be written as
hh ll mm instead of
AA BB hh CC DD ll mm.
If I were to breed that hypolavender motley to a diffuse opal (
aa dd ll), I would show the combined genes for the pair:
hypolavender motley -
AA hh DD ll mm
diffuse opal -
aa HH dd ll MM
The resulting offspring from this pairing would all be lavender het for amel, hypo, diffusion and motley (
Aa Hh Dd ll Mm) as the only morph gene that is the same in each parent is lavender. I will show this pairing in a Punnett square in my next reply. Right now, I need a cup of coffee!