Double Recessive Genetics 201

04 Aug Double Recessive Genetics 201

At this point we’ll assume that you’ve already read our Intro to Reptile Genetics & Simple Recessive Genetics 101 pages & are somewhat familiar with the terms we’ll be using going forward. Most of the genetic terms on this page are “clickable” and will bounce you back to the glossary page if you need to refresh your memory.

Note: In an effort to explain things really thoroughly, this page ended up being very long! Grab a snack (and a snake) and settle in for a bit! If you just want to jump ahead to the individual punnett square combos, there’s an opportunity to do so at the end of Section 1.

General Information

Double Recessive Gene Combinations – let the games (and headaches) begin!

Now that we’ve seen all the fun to be had with simple recessive color & pattern morphs, why not take things up a notch and start combining some of those cool genes to make even cooler ones? Before we used examples of single homozygous and heterozygous animals bred together. Let’s see what happens when we start crossing those homozygous traits.

Examples of Double Recessive Combinations in Reptiles

The following is a list of genetic mutations in reptiles that have been bred together to create double recessive combos. This list is not all-inclusive, but intended to give an idea of double recessive gene combos and their frequency in the herp world, as well as some of the popular species in which they are commonly found. As you can see, they are produced much more frequently in some species than others.

Ball Pythons Corn Snakes Burmese Pythons Boas Leopard Geckos
Caramel Glow Albino Motley Albino Granite Snow Albino Patternless
Snow Albino Blood Albino Patternless Albino Striped Banana Blizzard
Anery Striped Albino Labyrinth Albino Tangerine
Blizzard Patternless Tangerine
Ghost Hypomelanistic Albino
Motley Snow
Motley Stripe

Punnett Squares for Double Recessive Traits

Note: While we use ball pythons as our example here, the following punnet squares apply to any double recessive combinations in any species.

In the following punnett squares, we will demonstrate the various combinations for creating a Caramel Albino Orange Ghost ball python – aka the “Caramel Glow.”


  + =

Section 1: Understanding the results from breeding 2 different homozygous, recessive traits.

If we want to eventually produce an animal that is homozygous for two different traits, we have to start by somehow getting those different genes into the same snake. When breeding two homozygous animals for different morphs, we must remember that each gene will not have an effect on the other’s inheritance if they are not in the same locus. The gene that is mutated in the Caramel Albino is in a different place than the gene that affects melanin in an Orange Ghost (hypo). Keep in mind when calculating the sperm/egg possibilities for each parent, the “A” gene they get is independent of the “B” gene received. In this case we start by breeding a Caramel Albino (ccGG) to an Orange Ghost (CCgg), which gives us all normal-appearing, double-heterozygous offspring for both Caramel & Ghost (CcGg), as shown in the following punnett square:

Now that we have determined the genotype of the double-het offspring, we can look at various combinations for creating a visible double-homozygous mutation.

Double-het Caramel Glow X Double-het Caramel Glow

Since we now have 2 genes/4 different alleles floating around in each double-het, we must expand our punnett square to accommodate all of the possible combinations from each double-het parent. The 4 combinations from a single double-het are: CG, Cg, cG, & cg.

So we’ll take our two double-hets: CcGg & CcGg, and distribute them across & down the punnett square like this:

Now that we’ve distributed the genes across the punnett square, let’s go ahead & fill it in so we can see the outcome of breeding double-het to double-het.

For those who forgot their decoder rings:

CCGG = normal. Since there’s one of these shown, that means we have one normal-appearing, non-gene carrying critter in the lot.

CCGg = het Ghost. We produced 2 het Ghosts from the above pairing.

CcGG = het Caramel, and just like the het Ghosts there are two Caramel hets in this outcome.

CcGg = double-heterozygous for Caramel & Ghosts. 4 double-hets are shown in the punnett square.

CCgg = Ghost…just a “normal” Ghost, not het for anything. One in the resulting offspring.

ccGG = Caramel albino…and we see a pattern forming – just as there’s one “normal” Ghost (non-het), there’s also one homozygous (but not het Ghost) Caramel in this group as well.

ccGg = Caramel het Ghost. This is where it begins to get exciting – having a Caramel het Ghost will make the rest of the project go a bit faster, except there’s that little bit of figuring out which of the visible Caramels in this clutch is also het Ghost! There are two Caramel het Ghosts produced in this outcome.

Ccgg = Ghost het Caramel. As was just explained above with the Caramel het Ghosts, out of 16 offspring in a best-case-scenario, we should theoretically get two Ghosts het for Caramel from the above pairing of double-hets.

ccgg = PAYDIRT, BABY!! This is your actual, visible, double-homozygous animal – known in this case as a Caramel Glow (Carmel Ghost). There’s a one in 16 chance of this showing up in a double-het X double-het breeding, which is why herp breeders suffer bouts of hysteria & manic happiness when it happens, and ulcers and gray hair when it doesn’t.

“Well, wait a minute,” you’re probably thinking at this point…”ball pythons rarely lay 16-egg clutches, so wouldn’t my chances of producing a double-homozygous animal from 2 double-hets be pretty rare?” Obviously there are better chances of hitting a double-homozygous baby from a species known to produce large numbers of offspring, i.e. Burmese pythons, boas, retics, etc. By the same token, when breeding double hets, you’re also creating several different options to play with going forward – think about those visible Caramels het for Ghost and vice-versa. Sure, you’ll produce possible hets to play around with in the mean time, but don’t give up! Hitting that 1 in 16 is exhilirating!!

Now that we’ve seen the loooooong way into producing a double-homozygous animal, let’s look at some of the “shortcut” combinations, too.

Double-het Caramel Glow X Caramel

Moving on to our next genetic combination, we have a punnett square for the results from a Caramel (ccGG) ball python to a double-het Caramel/Ghost (CcGg) ball python breeding.

As we can see from the square, this breeding yields the following offspring:

4 het Caramels – CcGG

4 double-het Caramel/Ghosts – CcGg

4 Caramels – ccGG

4 Caramels het Ghost – ccGg

Once again, it will take some time & breeding to determine the Caramel-het-Ghosts from the Caramels, and the double-hets from the het-Caramels, but we also see more single homozygous animals from this pairing. These ratios would be the same for breeding a double-het Caramel Glow to a Ghost, except you’d have het Ghosts, homozygous Ghosts, and Ghosts het Caramel along with the double-hets.

Double-het Caramel Glow X Caramel het Ghost

Obviously breeding this combination of genes is a faster route to producing the double-homozygous Caramel Glow. Our results from breeding double-het to Caramel-het-Ghost are as follows:

CcGG = 2 het Caramels

CcGg – 4 double-het Caramel/Ghosts

Ccgg – 2 Ghosts-het-Caramel

ccGG – 2 Caramels

ccGg – 4 Caramels-het-ghost

ccgg – 2 Caramel Glows

Double-het Caramel Glow X Caramel Glow

This is where it starts to get fun, results-wise:

When breeding a double-het Caramel Glow to a Caramel Glow, the theoretical results should be:

CcGg = 4 double-het Caramel/Ghost

Ccgg = 4 Ghosts-het-Caramel

ccGg = 4 Caramels-het-Ghost

ccgg = 4 Caramel Glows

Nice & simple – no guesswork on possible hets, just beautiful snakes!

Double-het Caramel Glow X Normal

For our resident masochists, we decided to show a pairing that leads to a lot of guesswork & possible hets. When breeding a double-het Caramel Glow to a normal, wild type ball python, the results will be:

CCGG = 4 wild-type, normal, non-gene-carriers

CCgG = 4 normal appearing het-Ghosts

CcGG = 4 normal appearing het-Caramels

CcGg = 4 normal appearing double-het Caramel/Ghost


So as we see, the road to achieving a visible double-homozygous animal can be rather long, but it is as equally full of reward as it is frustration. Since you’re probably a bit overwhelmed with all of the possible genetic combos from breeding multiple recessive mutations together, why don’t you treat yourself to understanding projects with a bit more instant gratification by moseying over to our Co-Dominant/Dominant Genetics 301 page!

No Comments

Post A Comment

49 + = 59


Pradeep Aradhya brings a unique perspective to building commercial success in Technology, Fashion, Food and now Film. With the strategic approach of building a “minimum viable business” he guides Novus Laurus as well as mentors and invests in other businesses. Pradeep takes his experience in organic and inorganic growth strategies along with product and operational know how in multiple spaces and combines it with 12 years in digital marketing and the use of cutting edge technologies to drive businesses to “new successes”. Previously, as a senior executive he successfully led acquisitions in the mobile space where his role was to identify strategic growth areas, inorganic growth potential, candidate product companies and negotiate acquisitions. He has also led multi million dollar initiatives at Fortune 500 companies to create technology platforms for marketing. He identified and advocated the best and newest developments in various technology areas that gave brands competitive advantages in establishing lasting relationships with customers. Here at Novus Laurus he builds empowered and engaged teams both internally and within client businesses. Pradeep holds a Ph.D. in Structural Dynamics from NC State University and a M.Sc in Aerospace Engg. from the Indian Institute of Science.



Did you see our fantastic GALLERY yet?