One snake has one gene for Mojave and one for normal, the other snake has one gene for Spider and one for normal...

The offspring will get one gene from each parent.

If the offspring get one gene for mojave and one gene for spider, you'll get Spider Mojaves...

If the offspring get on gene for normal and one for mojave, then you'll get Mojaves...

If the offspring get one gene for normal and one gene for spider, then you'll get Spiders...

You have an equal chance of hitting all those... so you have as good of odds of getting spider mojaves as you do of getting normals.

And if the python gods hate you, then the offspring will get a gene for normal from each and you'll have all normals, and you have a 1 in 2 chance those normals will be boys... so be good and do something nice for the python gods NOW.

Bruce