Ball pythons, “Python regius”, come from Central Africa and are the smallest species of python (average length being 3-4 feet) on that continent. They are the only species of python to have a natural range that lies above the ecuador. In their natural range, they live in rodent burrows and live a nocturnal life style. Due to their small size and calm disposition, ball pythons have become popular as pets, and due to an influx of assorted color/pattern mutations over the past 20 years they have experienced a marked growth in popularity. Because of the wide variety and availability of color/pattern mutations of this species, ball pythons can make interesting subjects for genetics discussions. The pictures below represent a mere sample of the many color/pattern mutations that this species has to offer.
Bumblebee (Pastel x Spider): Heterozygous-Incomplete Dominant and Dominant
Albino: Simple Recessive
Genetic Stripe: Simple Recessive
Normal/Wild-type offspring from a dihybrid cross (Albino x Genetic Stripe)
The offspring from this clutch above resulted from a pairing between an albino female and a Genetic-Striped male, both of which are recessive traits. The offspring all display a normal looking phenotype but all carry the alleles to produce albinos, stripes, and even albino-stripes. Now according to Mendelian Genetics, if two of these offspring are mated back to each other, the resulting offspring of that pairing would result in a 9:3:3:1 phenotypic ratio (9=wild-type, 3=albino, 3=stripe, and 1=albino-stripe).
The dihybrid Punnett Square below shows all of the possible genotypes of this theoretical pairing. AA=Wild-type coloration, Aa=Wild-type coloration het. for albino, aa=albino coloration, PP=Wild-type pattern, Pp=Wild-type pattern het. for stripe, and pp=stripe pattern.
Patterns of inheritance:
The patterns of inheritance most commonly seen in ball pythons are,
and sometimes Co-dominance…
Sometimes when dealing with recessive mutations one has to perform a cross called a “Test Cross”.
A “test cross” is done when trying to determine the genotypes of two or more unknown organisms.
For instance, if we take two ball pythons that have a normal/wild-type phenotype but are both heterozygous for albino and breed them together, on average we should get 3 wild-types and 1 albino. Of the 3 wild-types, 2 of them will be heterozygous for albino but we have no way of knowing without perfoming a “test cross”. We can determine the genotypes of these 3 ball pythons by breeding them to ball pythons that we know for a fact are heterozygous for albino, or breed them to actual homozygous albino ball pythons. We can in turn determine their genotypes based on the phenotypes of their resulting offspring.
Videos of Real Life Genetics Probabilities
Here’s a short video of a clutch of ball python eggs being cut. This particular clutch was produced from crossing a male Butter to a female Pastel-Spider (Bumblebee). We cut this clutch to see how close we were to hitting the probability generated by the genetics wizard.
Now there were seven eggs in this clutch of eggs. Statistically, there were eight possibilities, all with an equal chance of happening, for the different color mutations and combinations. Our end results were 1 Butter-Pastel-Spider, 1 Butter-Spider, 1 Pastel-Spider, 1 Spider, 2 Butters and 1 Normal/Wild-type.
Here is a follow-up video to the one from above. In this video, we show all of the different ball pythons that hatched in this clutch. We also explain some of the color/pattern mutations seen in the clutch, their patterns of inheritance, and the probablility of actually getting the mutation.