here we go... from paulh here at faunaclassifieds:
I don't really get the difference between co-dominant and dominant in pastels, doesn't co-dom mean that it is made up of several genes to make the phenotype? Jaguars are considered co dom because more variation have been seen to come out of the gene. Pastels x normal you get 50 50, but isn't that because they only carry one of the paired genes, there is super pastels but i haven't seen any pics, do they look different then normal pastels or can you only tell they are super when you breed them out and get all pastel babies? Just wondering that, and if so wouldn't that make pastels dominate not co dom.
Unfortunately, many herpers have misunderstood the definitions of dominant, codominant, and heterozygous.
There are three possible pairings of genes at the pastel gene locus (location in the ball python genome). There may be a pair of normal genes (homozygous normal), a pair of pastel mutant genes (homozygous pastel), or a pastel mutant gene paired with a normal gene (heterozygous pastel).
Here are the definitions of dominant, codominant, and recessive mutant genes as used in standard genetics:
If a mutant gene is paired with a normal gene and the organism looks normal, then the mutant gene is recessive to the normal gene, making it a recessive mutant gene. Example -- the albino mutant gene in ball pythons.
If a mutant gene is paired with a normal gene and the organism looks like an individual with a pair of the mutant gene, then the mutant gene is dominant to the normal gene, making it a dominant mutant gene. There are no really good examples of a dominant mutant gene in snakes. Salmon in the boa constrictor and striped in the California king snake are dominant mutant genes, but both homozygous and heterozygous individuals show considerable variation in expression of the mutant appearance.
If a mutant gene is paired with a normal gene and the organism does not look normal but does not look like the individual with a pair of the mutant gene, then the mutant gene is codominant to the normal gene, making it a codominant mutant gene. Example -- the tiger mutant gene in reticulated pythons.
Most pastels available have a pastel mutant gene paired with a normal gene, making them heterozygous pastels. These are usually incorrectly called codominant pastels. NERD and others, I think, have produced some pastels that look distinctly different from the heterozygous pastels, at least as hatchlings. You might check the NERD web site for pictures. I don't know offhand whether any are old enough for breeding yet. Anyway, these are considered to be the super pastels, or homozygous pastels. They are incorrectly referred to as dominant pastels.
Pastel is either a dominant or codominant mutant gene. If the distinction in appearance between homozygous pastel and heterozygous pastel holds up, even if only as hatchlings, then it is a codominant mutant gene. If a significan number of homozygous pastels can only be identified through breeding tests, then pastel is a dominant mutant gene which shows variable expressivity.
Pastel (heterozygous pastel) x normal --> 1/2 normal, 1/2 pastel (heterozygous pastel). The normal snake produces sex cells carrying only the normal gene. Half of the heterozygous pastel's sex cells have the pastel mutant gene, and the other half of the heterozygous pastel's sex cells have the normal gene. If a normal gene is paired with a normal gene, the baby is normal. If a pastel gene is paired with a normal gene, the baby is heterozygous pastel.
Clear as mud?
Sorry, I know nothing about jaguars.
from the thread:
http://www.faunaclassifieds.com/forums/archive/index.php/t-59015.html
- damian
