Genetics

Snakes Incorporated · Joined: 02 Sep 2007 Posts: 10 Karma: 0 (0)

Genetics

A Crash Course In Genetics:
When reading about morphs and genealogy, it’s sometimes hard as a beginner to understand what is meant by phrases like:

100% Het
66% Het
50% Het
Heterozygous
Homozygous
Double Het
Triple Het
Poss

We’re going to break it down in simpler terms. Read slowly.
All genes are paired genes. Genes are either dominant or recessive (There IS such thing as co-dominant, but for argument sake, let’s skip that lesson until later). A dominant gene is a trait that’s shown. A recessive gene is a gene, that only when paired with another recessive gene, will it be seen. Let’s take brown-eyed people and blue-eyed people. The color brown in eyes is a dominant gene. The color blue in eyes is a recessive gene. When two alike genes are paired together, it’s called being Homozygous. Brown eyes will be labeled BB (homozygous for brown eyes) and blue eyes will be labeled bb (homozygous for blue eyes). When a brown-eyed person and a blue eyed person have children, the possible outcomes are:
B B
b Bb Bb
b Bb Bb

There are 4 possible outcomes, and as you can see they are all the same (Bb). What this will show is that any child born will have brown eyes. Even when brown is paired with blue, you will only see brown because brown is a dominant gene. But any child born from a brown-eyed and blue-eyed parent CARRIES the gene for blue eyes. This is called being Heterozygous for blue eyes. These children have a 100% possibility of being Heterozygous for blue eyes (4/4 = 100%). Now, when this is compared with, say, an Albino Ball Python, Albinism is the recessive gene. Albinism is a lack of all black pigment. RR will represent a regular Ball Python, and AA will represent an Albino Ball Python. When a regular and an albino are bred together, you will get:
A A
R RA RA
R RA RA

This means that all the snakes hatched will look normal, but will carry the gene for albinism. This is called being Heterozygous for Albino. Each snake hatched will have a 100% possibility of being Heterozygous for Albino (4/4 = 100%), or 100% Het Albino as is commonly referred to in the pet trade.
Now, if two 100% Hets were bred together, the outcome would be:
R A
R RR RA
A RA AA

This means that each egg has a 25% chance of being homozygous for Albino (1/4 = 25%), 25% chance of being homozygous for normal (1/4 = 25%), and 50% chance of being heterozygous (2/4 = 50%). Unfortunately, because Hets look like normals, we can’t be sure if they’re Hets or not. There are 4 possible outcomes demonstrated by the table above. Take the obvious albino away, now all that remains are 3 outcomes, 2 of which are het. So, when two 100% Hets are bred together, each hatchling that is normal looking has a 2 out of 3 chance of being heterozygous (2/3 = 66% Possibility), or 66% Poss Het Albino. The only way to positively prove a 66% Poss Het Albino is actually a carrier of the albino gene (which will prove it to be 100% Het Albino) is to breed it to an Albino:
A A
R RA RA
A AA AA

If it really is a carrier (RA), then statistically half the hatchlings will be albino and half will be normal looking. If the snake is not a carrier (RR), then all the offspring will look normal.

If a 100% Het Albino is bred to a normal, then the outcome would be:
R A
R RR RA
R RR RA

This means that each hatchling has a 50% chance of being normal and 50% chance of being a carrier. They will all look normal, so again, 2 out of the 4 outcomes are Hets (2/4 = 50% possibility), or 50% Poss Het Albino. Again, the only way to prove it really is a carrier is to breed it to an albino.

The reason any possible Hets should be bred to an albino to prove they really are carriers is that it eliminates other possibilities. You’re going to get Albinos and 100% Het Albinos if it’s a carrier, and only 100% Het Albinos if it’s not.
Though, if someone just wants to have a breeding project, possible Hets are much cheaper than 100% Hets and not much more expensive than a normals. The chance of getting albinos or any other morph will make the breeding project much more fun for any novice or hobbyist. The best project is to use one or two 100% Het males and a group of 66% or 50% Poss Het females. The morph you want will be floating around in there somewhere.

Heterozygous means a single copy of a gene out of two possible copies. A pastel is a heterozygous codom. A superpastel is a homozygous, which means it has two copies of the gene. Pastels are what you would call "visible hets" because a heterozygous animal is visibly different from a normal animal. The reason they are called CO-dominant, is because a homozygous animal is visibly different from a heterozygous animal.

albino black pastel x albino black pastel (or black pastel het albino) should be enough to produce super black pastel albino. :]

Wouldn't you use capital for the more dominant gene? I think that's why they use lower case for the mutant and upper case for the normal in recessive mutations. I think it gets switched with dominant mutations so that P would be the mutant and p the normal. There are lots of different notations though so hard to say one is more right. I'd also be tempted to use the same letter as part of a combination for all of these genes that are looking like alleles (different mutations of the same gene). Maybe W for white and something like this:

w = the normal version
Wl = the lesser version
Wp = the phantom version
Wm = the mojave version
Wb = the butter version
Wr = the Vin Russo version
Wd = the dilute version to make platy – apparently normal or near normal by it’s self

Having them all variations of "w" helps to remind you that (under the Hahaman allele theory) you can't have more than two of them - one from each parent. I'm looking forward to more interesting crosses to keep testing this but so far it holds up to every breeding I know of. Here are some notable combos

Wl w = lesser
Wl Wd = platy
Wl Wp = karma
Wl Wl = blue eyed leucistic with little or no back stripe
Wd w = normal looking platy offspring used to make more platies (could also use a platy)

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