Low expression jungles produce high expression jungles?

[Evenstar]

And that opens a whole can of worms. The Jungle gene in boas is technically an incomplete dominant gene. I have fallen into the bad habit of using the accepted term within the community, but, again technically speaking, it is incorrect. Here's why....

Incomplete dominance (def): a genetic situation in which one allele does not completely dominate another allele, and therefore results in a new phenotype.

The following is from the book, "The Complete Boa Constrictor" written by Vin Russo. Quotes are from pages 15-19.

Co-Dominance:

"When the recessive and dominant traits appear together in the phonotype of hybrid organisms, the expression is called CO-DOMINANT. When working with co-dominant traits, crossing organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together. This genetic scenario works in much the same way as incomplete dominance. A hybrid organism shows a third phenotype; not the usual dominant one and not the usual recessive one... but a third, different phenotype. With co-dominance we get a blending of the dominant and recessive traits so that the third phenotype exhibits both traits together. At the time of writing I am not aware of any boa traits that have been proven to be co-dominant."

Incomplete Dominance:

"For many years, reptile breeders have erroneously used the term "co-dominant" when in reality they are referring to INCOMPLETE DOMINANCE. Incomplete dominance is similar to a recessive trait, in that the heterozygous offspring are gene carriers for a specific trait. However, in breeding scenarios where incomplete dominance is involved the heterozygous animals have a visual indicator therefore are referred as "visually heterozygous". This means the offspring exhibit another type of color or pattern that is halfway between the normal appearance and the "super" or more exaggerated dominant form. So if you breed boas to each other that have an incomplete dominant trait and that are visually heterozygous for an extreme trait, you will have a one in four chance of producing the super, exaggerated form which will be dominant. When this dominant boa is then bred to a normal, all of the litter will be visually het. offspring. And finally if you breed these visual hets to a normal you will get half visual hets and half normal appearing boas.

With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of both parental traits. An example of this genetic phenomenon that is easy to remember is the crossing of a red flower (dominant) with a white flower (recessive). Incomplete dominance in such a cross will produce all PINK flowers. Another way to think of it is that it is like mixing two colors of paint. An example of the incomplete dominant trait in boas is hypomelanism. This trait is quite common amongst Central American boas and the best known example was popularized by Rich Ihle. He named this trait "salmon hypo boa" for its underlying salmon colors. This trait is incompletely dominant because the super form is very light and exhibits very little or no black at all, and the visually het is a little darker an is visually distinguished as being something between the normal and a super." The same is true for the Jungle gene - there is a super form of Jungle.

Here's the kicker - consider things from the perspective of the Dominant phenotype (the super form, ie: super hypo or super jungle) "When this super hypo (the dominant or red flower) is bred to a normal appearing boa (white flower) the result is all hypo boas (pink flowers). The hypo boas (pink flowers) are now heterozygous for the super hypo trait. However, they are VISIBLE heterozygous boas because they are also hypomelanistic - but not as exaggerated as the dominant super form. Therefore, they are a blend of both traits (pink flowers)."

The super form of Jungles have issues with reproduction. It is exceedingly rare for a super-jungle to have the ability to reproduce. In fact, I am aware of only ONE super-jungle in existence that has been successfully bred and, in actuality, that litter has not even dropped yet so the results are still as yet unknown.

As a result, breeders don't often work with super jungles. Nor are jungles often bred together, making more supers. Because the gene is a dominant trait, a Jungle bred to a normal will produce more Jungles - and this is where the gene manifests it's unusual characteristics - the visual heterozygous form is capable of not only reproducing itself, but producing "better" than itself. What causes two Jungles from the same litter for one to be low-expression and the other to be wild and crazy?? What allows a low-expression parent to produce wild offspring?? There is far more to genetics than meets the eye....


If you don't have it already, I highly recommend you get the Vin Russo's book mentioned above. It is expensive, but well worth it. It is the boa keeper's bible. You can order it directly from Vin's website: http://www.cuttingedgeherp.com/books.html