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Determining if a trait is Mendelian

This is a section from the Cornsnake Morph Guide which explains the process of proving out a new gene. You can use the flowchart below, or you can answer yes/no type of questions about your test breedings in order to find out how to proceed. If you find an interesting looking specimen at a show or hatch something odd yourself, and you want to find out if you can make more in a reliable way, this is how you go about proving the existence of a dominant, codominant, or recessive gene that controls that appearance. Or you end up proving that it isn't, which is also useful information.

Step 1:

Breed Mutant to an unrelated, typical, run-of-the-mill specimen.

    Notes:

  • Do not use anything that looks like the mutant. This will ensure that, if you are lucky enough to hatch more offspring like them, you cannot tell why.
  • Do not use anything that may potentially mask the expression of the presumed gene. If you are trying to see if a gene reduces red pigment, don't use an anerythristic.
Proceed to step 2





This flowchart describs the process of test breedings needed in order to determine if a trait is inherited in a mendelian fashion. Step 1, breed to an unrelated, typical normal corn. Step2, you look for mutant offspring. If there are some mutant offspring proceed to Step 7, where you breed F1 mutant to an unrelated normal as well as F1 mutant to F1 mutant. If the results of these show that the trait is either fully present or fully absent it is a mendelian dominant if there are only two phenotypes, or codominant trait if there are three clear phenotypes. Alternately if the results are many variations with some more mutant-looking and others more normal-looking, it is not a mendelian trait. If in step 2 all of the offspring look normal, then proceed to breeding F1 X F1. If this results in fully normal offspring and fully mutant offspring, with no 'between' offspring, it is a mendelian recessive trait. Otherwise if you have hatched 20 or more with no success it is probably not a menedlian trait. If in step 2 the offspring take on appearances with many variations, some more mutant-looking and others more normal-looking, it is not a mendelian trait, but it is worth rethinking your method of identifying them to see if some aspect of them is in fact either expressed or not in any particular specimen.


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