Professional Herpetoculture for the Pet Trade

Genetics 601 - Using What You've Learned

Ok, so you've read all the previous pages and feel like you understand it all (more or less) but you still don't know how to apply it to the problem in hand. In other words, you still don't know how to tell what you'll get when you breed your Amel Motley Cornsnake, het for Caramel to your Butter Motley Cornsnake. Well, you are not alone, and you are not stupid.

While all of this genetics stuff may seem complicated, it's really no harder than anything else you've learned. Take mathematics for instance. Once you learned the basic rules of addition, and did enough practice to let it all sink in, you could add any two numbers together - no matter how large and complicated seeming. Genetics is no different.

Here's how to do it:

Step One

To predict any outcome from any breeding, you must understand what traits are actually present in the parents. To proceed, you MUST research the trade name you are familiar with (here Amel Motley, het Caramel and Butter Motley) to find out what traits these morphs are actually composed of.

In our example above, you must forget that one parent is an Amel Motley Cornsnake, het for Caramel and the other is a Butter Motley Cornsnake. Names like that are meaningless, genetically speaking.

Instead, you must learn to view them as a Cornsnake that is homozygous for Amelanism, homozygous for Motley, and heterozygous for Caramel and a Cornsnake that is homozygous for Amelanism, homozygous for Motley, and homozygous for Caramel.

Do this for every locus containing a mutated allele in either parent (in this case three alleles at three loci total). While you are at it, learn the commonly used genetic connotations (abbreviations) in use for each trait.

Parent 2) Amel Motley, het Caramel Cornsnake (aaaa·mmmm·Ca+cac)

  • Amelanism, homozygous - abbreviated as: aaaa
  • Motley, homozygous - abbreviated as: mmmm
  • Caramel, heterozygous - abbreviated as: Ca+cac


Parent 2) Butter Motley Cornsnake (aaaa·mmmm·Caccac)

  • Amelanism, homozygous - abbreviated as: aaaa
  • Motley, homozygous - abbreviated as: mmmm
  • Caramel, homozygous - abbreviated as: Caccac

Step Two

You must treat each Locus separately when predicting the outcome for the breeding. In our example, we have three alleles residing at three separate loci - so we'll be doing three separate calculations, one for each loci.

For our example, we'll simply list each locus and place the alleles present there from each parent side-by-side, like this:

  • At the Amel Locus (A), we have: aa aa
  • At the Motley Locus (M), we have: mm mm
  • At the Caramel Locus (Ca), we have: +c cc

Step Three

Then we'll use our simplified FOIL technique to tabulate the results at each locus. We could create a Punnett Square for each trait, but FOIL is quicker once learned. FOIL is an anachronism for First pair, Outside pair, Inside pair, and Last pair. Remember, one allele is passed from each parent and FOIL will help us quickly determine the four possible combinations for each locus. It works like this, and here we've highlighted each pair from the first locus in red for you:

  • Amel Locus (A) aa aa First Pair
  • Amel Locus (A) aa aa Outside Pair
  • Amel Locus (A) aa aa Inside Pair
  • Amel Locus (A) aa aa Last Pair


In this example, we have: aa, aa, aa, aa.

Now we'll repeat this for the next locus:

  • Motley Locus (M) mm mm First Pair
  • Motley Locus (M) mm mm Outside Pair
  • Motley Locus (M) mm mm Inside Pair
  • Motley Locus (M) mm mm Last Pair


In this example, we have: mm, mm, mm, mm.

Now we'll repeat this for the last locus:

  • Caramel Locus (Ca) +c cc First Pair
  • Caramel Locus (Ca) +c cc Outside Pair
  • Caramel Locus (Ca) +c cc Inside Pair
  • Caramel Locus (Ca) +c cc Last Pair


In this example, we have: +c, +c, cc, cc.

Step Four

Now we combine the results of the first two alleles (Amel and Motley) by using a simple grid, much like that of the Punnett Square.

First, place the results of FOIL for the first allele along the left side:

         
aa        
aa        
aa        
aa        


Next, place the results of FOIL for the second allele along the top:

  mm mm mm mm
aa
aa        
aa        
aa        


Finally, fill in the grid with the results:

  mm mm mm mm
aa aamm aamm aamm aamm
aa aamm aamm aamm aamm
aa aamm aamm aamm aamm
aa aamm aamm aamm aamm


To add in the results of the third allele, we now create another grid. This time, place the results of the first grid along the left side:

         
aamm
aamm        
aamm        
aamm        
aamm
aamm        
aamm        
aamm        
aamm
aamm        
aamm        
aamm        
aamm
aamm        
aamm        
aamm        


Next, place the results of FOIL for the third allele along the top.

Notice that in this example, all results along the left side are the same. Therefore, we can simplify our task by combining the results into one row. Not all breedings will allow you to do this, but most will to at least some degree. Now our grid should look like this:

  +c +c cc cc
aamm


Finally, fill in the grid with the results:

  +c +c cc cc
aamm aamm+c aamm+c aammcc aammcc


Now, we can see the results of our breeding!

We've produced two types: aamm+c and aammcc. We can also see these are produced in a half and half ratio.

By reinserting the connotations for each locus, we get: aaaa·mmmm·Ca+cac and aaaa·mmmm·Caccac

In other words, these two types are:

Cornsnakes that are homozygous for Amel, homozygous for Motley, and heterozygous for Caramel and Cornsnakes that are homozygous for Amel, homozygous for Motley, and homozygous for Caramel.

Or if you insist on going back to those confusing but all too familiar trade names, we've produced a clutch containing half Amel Motleys, het for Caramel and half Butter Motleys. Not bad for a day's work!

Questions, questions, questions

Ok, so I've showed you how to do it. Let me guess you still have a gazillion questions, right? Let's try to answer some of the common ones here:

Q: I have a total of five traits in my breeding, how do I figure this when your example only has three?

A: No problem. Follow along exactly as I showed you. When you get to the end, create yet another grid - placing the results you just obtained in the left hand column just as before. Now FOIL allele number four and place it at the top. Figure out the results and you will now have all the combinations possible for four alleles. Repeat the whole thing again for trait number five....six...seven...whatever.

Q: My snake contains a trait that's incomplete dominant, how does that affect the outcome?

A: It doesn't. Such traits are still passed along in the exact same fashion, and can still be predicted 100% accurately using the method we just showed you. The only thing different about such traits is that specimens heterozygous for the trait will be visibly distinguishable from normals. Specimens homozygous for the trait will have still another appearance, usually even more drastically different from normal.

Q: My snake contains a trait that I'm told is a selected trait, how does that affect the outcome?

A: Well, the truth is that selected (polygenic) traits just don't work this way. Well, actually they do, but they are composed of perhaps dozens of alleles, each of which contribute to the overall appearance, many of which cannot be identified by themselves. Thus the results cannot be accurately predicted. Go back a page to Genetics 501 and review the information there on polygenic traits until it sinks in. But remember, you can still use this method to predict the outcome of crosses to typical mutations, you'll just have to sort through the babies for a few generations to fully regain the desired appearance.

Q: Why didn't my clutch hatch out to match the predictions?

A: While this method does predict the correct ratios and types of offspring that will result, mother nature still has her quirks. These predictions are just averages, and it can take a LOT of hatchings to make the numbers work out. Just because one in sixteen eggs is supposed to be a rare yellow-spotted stump-whumper, doesn't mean egg number sixteen is going to be one. In fact, you may go hundreds of hatchlings before a dozen of them suddenly appear in one clutch. That happens to us quite often, and of course the opposite often happens as well, but never to us. I'll put up a page on Murphy's Law if you really can't understand how that can be. There are also other potential factors which can account for this, such as trait linkage, sex linkage and so forth. Go back to Genetics 501 to learn more about these subjects.

Q: My clutch produced types of specimens not included the predictions, what happened?

A: Well, in today's herp marketplace, it seems nearly every specimen sold is carrying hidden traits of some sort. Rare indeed is the breeder that has full knowledge of every trait present in every specimen in their colonies! Yours have now been proven to be no exception! The thing to do now is realize that two situations exist: If neither parent exhibits the trait in question, then both parents are heterozygous for it. If only one parent exhibits the trait in question, the other has now been proven to be heterozygous for it. Go back to step one, using the new information you have just learned, and recalculate the whole thing. Your results will now be correct.

Q: My question isn't answered here, what do I do?

A: Well, write me about it silly. I'll even include it here for others who may have the same question!