“Reptile genetics can be confusing and hard to comprehend. Our intention for this section is to hopefully shed some light on that confusion, and educate future breeders and buyers alike.

In the near future we will be adding specific tabs to our basics “Genetics” page explaining the common terms, and mutations that are available. We will also give an in depth diagnosis of our experiences and results from breeding using various genotypes and phenotypes. The results can be viewed and guided from within this ‘Genetics‘ section.


Below are some common terms and their meanings you will probably come across throughout the site and also when discussing morphs in general.

Albino – having absent or deficient melanin. Widely used term for “amelanistic”. See tyrosinase-negative and tyrosinase-positive.

Allele – either of the two paired genes which affect an inheritable trait.

Amelanistic – having no melanin.

Anerythristic – having no red color.

Axanthic – having no yellow color.

Codominant – a gene that causes the homozygous form to look different than the wild-type and the heterozygous form to have traits of both.

DNA (Deoxyribonucleic Acid) – molecules bearing genetic information of all living cells. Gene. Also referred to as “unit of inheritance.”

Dominant – a gene that causes an animal to look different than the wild-type and where the homozygous form and the heterozygous form look the same as each other.

Double Heterozygous – being heterozygous for two different traits.

Gene – unit of heredity that determines the characteristics of the offspring.

Genetics – the study of heredity.

Genotype – an organism’s genetic composition. Heredity – the transmission of genetic characters from parents to offspring.

Het – an abbreviation for heterozygous.

Heterozygous – possessing two different genes for a given trait. An animal with one mutated, recessive gene still appears normal; its mutated gene can be inherited by future offspring. A codominant animal is heterozygous for the dominant form of its mutated gene, yet is different in appearance than both the wild-type and homozygous forms.

Homozygous – A state in which both genes for a specific trait are the same. When a recessive gene is it its homozygous form, it makes the animal look different from the wild-type. When a dominant gene is in its homozygous state, it causes the animal to look different from both the wild-type and the heterozygous (codominant) forms.

Hypomelanistic – an animal having less black and/or brown color than a wild-type.

Leucistic – a pure white animal with dark eyes.

Locus – a gene’s position on a chromosome (plural: loci)

Melanin – black or brown skin pigments.

Melanistic – abnormally dark, especially due to an increase of melanin.

Mutation – an abnormal gene that under certain circumstances can cause an animal to be born with an appearance other than wild-type.

Normal – an animal with no mutated genes – “wild type” in appearance. (See wild type)

Phenotype – an animal’s external apperance, as caused by its genotype.

Possible Het – an animal from a known breeding that has either a 50% or 66% possibility of being “heterozygous” for a mutant gene.

A 66% possible het comes from breeding 2 heterozygous animals together: 50% of the offspring are heterozygous, 25% will be homozygous, and 25% will be wild-type. Of the normal appearing animals, 66% (or roughly 2 out of 3) will actually be heterozygous for the mutated gene.

A 50% possible het comes from breeding a heterozygous animal to a wild-type animal. All of the resulting offspring will be wild-type in appearance, but 50% of them will actually be heterozygous for the mutated gene and must be bred out to determine which animals are really hets.

Recessive – a gene that affects an animal’s appearance if it’s present in the homozygous state. A heterozygous animal carrying a mutated, recessive gene looks normal.

Super   commonly used herpetocultural term for the dominant form of a co-dominant mutation. i.e. Super Pastel

Tyrosinase – an enzyme required for synthesizing melanin.

Tyrosinase-negative – an albino whose cells lack tyrosinase, producing a white and yellow/orange animal with pink eyes. A separate albino mutation from tyrosinase-positive. Also called T- .

Tyrosinase-positive – an albino not able to synthesize melanin, but capable of synthesizing tyrosinase, which results in lavender-brown skin color. Also referred to as T+ .

Wild-type – the way the animal usually looks in nature (i.e. the normal color and pattern).
Xanthic – having more yellow color than wild-type.

Punnet Squares



Simple Recessive
Simple recessive traits are proven, inheritable genes that are only visible in their homozygous form.
When a homozygous animal is bred to a wild type (normal), non-gene-carrying animal, all of their resulting offspring will be normal in appearance, but will carry the gene from the homozygous parent. This is due to a mutated allele being passed on from the homozygous parent to the offspring, and a normal allele being passed on by the wild type parent. Since the two alleles are different, they dictate that the offspring’s phenotype will be normal, while their genotype is heterozygous. These offspring are known as “heterozygous” or simply “hets.” To reiterate, the offspring carry a genetic code for the mutation but are not visibly different from a normal, or wild type, animal.
Some examples of Simple Recessive Traits in Carpet Pythons are Albino, Axanthic and Granite.

Normal X Homozygous Parents
Here we’ll demonstrate a punnet square to show the resulting offspring from breeding a Normal/wild type carpet python (NN) to an Albino carpet python (aa).
As we can see from the above square, all of the offspring from breeding a Normal to an Albino will be normal in appearance, but carry the gene for albinism (Na). The offspring are all 100% heterozygous (Na) for albino, otherwise known as “definite hets.”

Normal X Heterozygous Parents
This punnet square shows the offspring from breeding a 100% heterozygous for albino (Na) carpet python to a Normal/wild type (NN) carpet python.
From this pairing of heterozygous (Na) to Normal (NN), we can see that all of the offspring will be normal in appearance, but half of them will be heterozygous for albino (Na). Breeding hets to normals produces what are known as “50% possible hets.” Since half of the offspring are hets, but all of them are normal in appearance, you have a 50% chance of the animal you pick from that clutch actually being a heterozygous (Na) animal. The fastest way to prove which of the offspring are definite hets (Na) is to breed them back to a homozygous (aa) animal. If the animal you picked was one of the definite hets, then you should theoretically see a homozygous (aa) animal (in this case, an albino) in their offspring.

Heterozygous X Heterozygous Parents
Moving on to our next genetic combination, we have a punnet square for the results from a het for albino (Na) carpet python to het for albino (Na) carpet python breeding.
Out of the four offspring shown in this square, we see one normal/wild-type/non-gene-carrying animal (NN), two heterozygous animals (Na), and one albino (aa) animal. Just like with the normal-to-het breeding shown above, the two hets (Na) and one wild type (NN) snakes from this pairing are all normal in appearance, so it is impossible to tell which animals are the hets. Since approximately 2/3 (or 66%) of the normal appearing offspring in this clutch are actual hets for albino, they are labeled as “66% possible hets.”

As we can see here, breeding hets together can be a very feasible way to produce a homozygous animal. Hets are a great way to get into some of the higher-end projects, since they’re typically much less expensive than the homozygous forms.

Heterozygous X Homozygous Parents
Here we explore another “instant gratification” combo: breeding a het albino (Na) carpet python to an albino (aa) carpet python. As we’ll see from the punnett square, this pairing produces homozygous animals.
What a great combo this is!! According to our punnett square, out of the four resulting offspring two will be het for albino (Na) and two will be homozygous albinos (aa)! Since one of the parents was a homozygous (aa) animal, all of the normal-appearing offspring will be 100% hets (Na) – no guesswork involved.

Homozygous X Homozygous Parents
 Our final punnett square is very straightforward. Just as two completely normal, wild-type (NN) animals will produce all normal, wild-type (NN) offspring, two homozygous albino (aa) carpet pythons bred together will produce all homozygous albino (aa) offspring.