Posted by:
Paul Hollander
at Tue Apr 18 18:49:09 2006 [ Email Message ] [ Show All Posts by Paul Hollander ]
I'd like to make a few modifications here.
>As I understand it, Pastel is a specific line of Hypo.
As I understand it, Pastel is a line of boas selectively bred for less than normal black pigment. There are probably many genes involved, with each gene having a small, additive effect. On the other hand, the salmon (hypo) mutant gene is a single mutant gene that produces a fairly obvious effect.
>Hypo is a dominant trait.
A trait is a difference from what we'd see in a wild type or normal boa constrictor, which is the type we'd expect to see in the pet trade. We can look at a snake that shows the hypo trait and say that it has less black pigment than a normal snake. Genes are inside the cells and are invisible to the naked eye. 
A gene is a unit of heredity, made up of DNA. See
http://en.wikipedia.org/wiki/Gene
for a more complete definition of a gene.
The terms "dominant", "codominant", and "recessive" should be applied to the gene and not the trait. This can often be confusing because the trait and the gene have the same name.
By the way, "dominate" and "co-dominate" are common mispellings of "dominant" and "codominant".
>Het = heterozygous = having one gene within a gene pair, ie het for albino means having one albine gene and one normal gene. Also applies to dominant traits like hypo, het hypo woulod mean one hypo and one normal gene but since Hypo is dominant, the animal looks hypo.
You can't have only one gene in a gene pair. There are two genes in a gene pair. A gene pair is heterozygous whenever the two genes are different. Most commonly, one gene is a normal gene, and the other gene is a mutant gene. But sometimes both genes are mutant genes, as long as they are different mutant genes.
>Homozygous = having both genes within a gene pair the same. Hom for albino would have two albino genes and look albino. Hom for hypo would have two genes for hypo and look hypo.
This is correct, though it's best to stop after "Homozygous = having both genes within a gene pair the same."
>Dominant = trait where there are not significant 100% distinguishable traits between the het and hom animals
Change the first "trait" to "gene", and the definition is right. In salmon (hypo) boas, it is often hard to tell the difference between a snake with two salmon genes (homozygous salmon) and a snake with a salmon gene paired with a normal gene (heterozygous salmon). This makes the salmon gene a dominant mutant gene.
>Co-dominant = Trait where the Het and Hom animals are 100% identifiable.
Codominant. Change "trait" to "gene", and the definition is right.
Recessive = A mutant gene that produces a detectable effect only when homozygous. The heterozygous animal looks normal.
In practice, sometimes the heterozygous animal can be identified when it isn't expected to identifiable. In these cases, the gene is assigned to the category where there is the best fit, even if not an exact fit. Salmon (hypo) is one of the mutants that doesn't exactly fit either the dominant or codominant category. That's why you might see one person call it a dominant mutant and another call it a codominant mutant. In my opinion, it fits the "dominant" category better than the "codominant" category.
>Ghost is Hypo/Anerythristic. Could be het for hypo/hom for anerythristic or hom for both and still look basically the same.
Yes.
>A "double het for ghost" would have one hypo gene and one anery gene and would look like a normal hypo.
Better would be as follows: A "double het for ghost" would have one hypo gene paired with a normal gene and one anery gene paired with a normal gene. This boa would look like a hypo because the anerythristic mutant gene is recessive to the normal version of the gene and the salmon (hypo) mutant gene is dominant to the normal version of the gene. By the way, the normal version of the salmon gene is not the same as the normal version of the anerythristic gene. The two normal genes have different DNA structure and different locations in the chromosomes.
A DH het ghost isn't really a ghost. It's pretty easy to get a DH het ghost by mating a salmon to an anerythristic. To get a ghost, both parents must have at least one anerythristic mutant gene, and at least one parent must be a hypo, too. Matings that would produce ghosts:
DH het ghost x het anerythristic --> 1/8 ghost
DH het ghost x anerythristic --> 1/4 ghost
DH het ghost x DH het ghost --> 3/16 ghost
DH het ghost x ghost --> 1/4 ghost
ghost x het anerythristic --> 1/4 ghost
ghost x anerythristic --> 1/2 ghost
ghost x ghost --> 3/4 ghost
If price is a measure of rarity, compare the prices of the parents in these seven matings against the price of a hypo and an anerythristic.
A triple het has three gene pairs that are heterozygous. As humans have something like 20,000 gene pairs, and snakes can't be terribly far behind, there is a lot of opportunity to have heterozygous gene pairs. When I was breeding ringneck doves, five heterozygous gene pairs was fairly common, and sometimes I got up to eight.
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RE: anyone explain the pastel trait to m - Paul Hollander, Tue Apr 18 18:49:09 2006