Basic Genetics Information (Bullsnakes Highlighted) (2024)

This page is designed to be a BASIC introduction to genetics. We assume that you understand the basics of Mendelian Genetics. If you need a refresher, we recommend spending some time reading through various forums to familiarize yourself with basic terminology. THIS website is a good description of basic genetic terminology that we are concerned with and you may come across when breeding reptiles. THIS website is a good glossary of genetics terms that is extremely useful too.

BRIEFLY: Most of the traits that we are concerned with in herpetoculture (non-ball python breeding) are simple recessive genes. This means that in order to display a given mutation (e.g. albino) the animal must carry two (2) copies of that gene. If it carries a single copy of the albino gene, that individual would be 100% heterozygous for albino. There are also genes that are co-dominant, but these will not be discussed here. Refer to the pages linked above for more information about these types of genes.

EXCELLENT website with TONS of information about bull snakes and other Pituophis spp (http://slitherbriggs.webs.com/pcsayi.htm).

When breeding many of the species common in herpetoculture today, you will have a number of morphs available to use. This genetics calculator example is based on the calculatordesignedand published by Marcel Poots. One of the main species in my breeding group isbullsnakes (Pituophis catenifer sayi). This species of Pituophis currently has 7 proven simple recessive genes available for purchase (current as of April 2014). This leads to a myriad of different combination morphs that can be created. Below I have provided a link to the genetics calculator referenced above along with a file I created specific to bullsnakes. I created this file and made it available to everyone so they can predict the outcomes of their breedings. Keep in mind that these are the average results and that your results may vary greatly in a given clutch. Below are a series of screen shots showing how to predict the genetics your clutch. The bullsnake specific file will be updated to reflect new genes as they become available.

Below are a series of screen shots showing you how to use the program and the bull snake file we have created. To start you need to download the MP Generic Genetic Wizard (below and HERE). Once you have the file downloaded you will need to unzip the file. There are lots of programs available for unziping compressed files, the one we typically use is 7zip, but use any program you want to unpackage the genetics wizard.

Once you have the wizard unpackaged you will need to move this folder to a location on your "C:" drive where you will not accidentally delete it (remember where you put this folder!). Once the folder is there, create a desktop shortcut to the "GenericGenWiz" application link. Now you are good to go with the remainder of the instructions below.

The next few screen captures will navigate you through the basic workings of the program. The "Gene management" (green box above) includes all of the known simple recessive mutations in bull snakes (red box above). Each gene has three possible options for expression in the genotype/phenotype (normal, visual, and heterozygous). Finally, each gene can have its "strength" set. This is mainly important if you have co-inheritance or incomplete dominance (see webpages linked above for definitions). Luckily, there are none of these genes proven in bull snakes. Additionally, the combinations of all these genes are listed on the far right of the program (blue box).

This is all already set up for you in the bull snake.ini file so you do not need to change anything here.

Now that you understand the set-up information regarding gene management, you can utilize the program to predict your breeding outcomes. To do this select the "Calculation" tab (green box), located immediately to the right of the gene management tab. Once you open the calculation tab, you will notice that the portion of the window to the far right has now changed to have "male" and "female" tabs. Click on the male tab (red box) and enter the genetics for your male/sire. For each visual trait that he displays you will select that trait's name from the drop down to the left of the gene. For example, in my screen capture, my hypothetical male is a visual anery/axanthic (Miami Co.). If I stop there, this is the only gene the male will contribute to the planned breeding. If the male is 100% heterozygous for a trait you would select "het xxxx" from the drop down men.

Additionally, you can manually enter the genes (symbols correspond to the symbol found under gene management) into the appropriate location under calculation (blue box on the left)

Using the same method described above, enter the female's/dam's genetics (red box). Again, this can also be done manually (blue box).

At this point, you can see the predicted outcomes of your breeding. In the example above, I have entered a breeding between an anery(Miami co) whiteside het hypo (Trumbower) male (bb+hww, blue box) and an hypo (Trumbower) het anery (Miami Co) and het whiteside female (+bhh+w, blue box). Be sure to select "Single genes" from the options (black box). The program has trouble with displaying gene combinations if they are too long, "Singe genes" avoids this issue. You can also see the genetics of your breeding pair listed at the top of the predicted outcomes frame (orange box). If you are interested in the actualpunnetsquare, you can find it in the bottom frame (yellow box).

The "Genotype" vs. "Phenotype" option allows you to see the hets (both 100% and less than 100%) that your offspring would carry. Above you can see that because the male is visual anery and whiteside all of the offspring are 100% het for both (if they are not visual). The same is true for hypo, because the female was visual for it. If you are breeding a 100% het animal to a normal, all of your offspring would be 50% possible het for that trait. Unfortunately, there is no way to tell which carry the gene and which do not without breeding those offspring to a visual in the future.

By comparing the above screen capture with the previous one, you can see that when you select "Phenotype" you will only get results that show the visual traits you babies will display.

The remaining two options are: changing the display to "Percentage" from "Ratio (Black box) and displaying possible hets or not (Show Poss vs. No poss hets; Purple box).

The ratio vs. percentage option is pretty straight forward. In selecting percentage, you will see the percentage of your clutch that will display the given genotype. Compare this to the previous screens where the ratio of the clutch was shown. This shows the exact same thing, but one may be easier for you to wrap your head around than the other (I prefer percentage).

The displaying possible hets comes into play if one of your breeding adults is 100% het for a trait/gene but the other adult is normal for the same trait (i.e. doesn't carry the gene). In this situation, you can see that your offspring each had a 50% chance of receiving a copy of that gene. Again, there is no way to know which ones have the gene (and are 100% het) and which ones did not get the gene (and are 0% het or normal). A similar situation happensif both of your adults are 100% het (thereby producing 66% hets).