Reptile & Amphibian Forums

Can someone tell me what that means? Specifically waht it would mean for an albino.

simply put, and ill use albino as an example...it means the animals carry half the genes needed to make albinos. the animals appear normal but when bred to another het each egg has a 25% of being totally normal, a 25% of being albino, or a 50% chance of being heterozygous for albino. when a het (short for heterozygous)is bred to a normal youve got a 50 - 50 chance of hatchling hets (making them possible hets). and when a het is bred to an albino each egg has a 50 - 50 chance of being a het or being albino....remember these are for EACH egg, not the whole clutch. hope i helped

J
-----
Jaymz
"got a bowlin ball in my stomache, got a desert in my mouth. figures that my courage would choose to sell out now..."

Yeah that helped a lot thank you

I'd start a little farther back.

Genes come in pairs. Heterozygous simply means that the two genes in the pair are not the same. For example, one albino mutant gene paired with one normal gene. Homozygous means the two genes in the pair are the same. For example, two albino genes or two normal genes.

Those breeding results are correct when a recessive mutant, such as albino, is heterozygous. Breeding results for heterozygous animals are a little different when the mutant gene is dominant or codominant to the normal form of the gene.

Paul Hollander

"to carry a gene but not show it outwardly....."

the gene is hidden....(as they said....half complete.......).

........to carry a gene and show it is te "homozygus" term.......

.........

JY

I know this is how it works in recessive mutations but I believe that this sort of thinking is confusing when we start getting into co-dominant and dominant. If you go back to the text book definitions then it isn't difficult to follow that pastels and spiders (at least most of them) are hets that do show.

hmmmmmm.....didn't think of the co-dom crap

to me......pastel would be a morph with no hets.......yet super pastel would be double pastel?.......LOL

I'll leave it to You"all to explain it.....I haven't read a book in awhile.....and never met a biologist or a real educated person at a reptile expo(except Dave Barker ,sorry).......

(alot of smart people as far as breeding for numbers......)

I am not [bleep]in....for real......haven't bought a book in years......I just haven't found a good one in awhile..........

.........pastel is het for super.......yes.......but it is a morph in itself to me(you all)......and actually the more affordable........LOL.......(probably more beautiful?).....

.........what was the topic?..........LOL..........

gone....have fun...........JY

I find that it helps me to remember the textbook definitions that Paul posted:

Heterozygous = unmatched pair of genes
Homozygous = matched pair of genes

If you get hung up on thinking about how the phenotypes (appearances) come out with a recessive mutation such as albino it's easy to get mixed up when you start throwing in dominant and co-dominant mutations. For me, it works to remember the rules for genotype inheritance since the rules are always the same and then figure out the phenotypes later based on what type of mutation it is. Here are the rules for the 5 types of genotype crosses (chance is for each baby, not a guarantee of what types you will find in any clutch):

1. Normal X Normal = 100% normal
2. Heterozygous X Normal = 50% chance heterozygous, 50% chance normal
3. Heterozygous X Heterozygous = 25% chance homozygous, 50% chance heterozygous, 25% chance normal
4. Homozygous X Heterozygous = 50% chance homozygous, 50% chance heterozygous
5. Homozygous X Homozygous = 100% homozygous

If you can remember those basic rules then all you need to do is remember the phenotypes for each mutant type and you can figure anything out. Here are the rules for the three types of mutations we have seen so far. We might eventually also see sex linked which gets really wild.

A. Recessive: Heterozygous is normal phenotype, only homozygous is mutant phenotype. Example - a heterozygous albino looks normal, only an animal with two albino genes (homozygous albino) looks albino.

B. Co-dominant (some say this should really be called “incompletely dominant” but regardless of which is more correct “co-dominant” is firmly established in the trade): Heterozygous is different from normal but homozygous is different yet. Example - a jungle pastel is a heterozygous super pastel (homozygous form).

Note: I think if we ever find a mutant gene that is fatal when homozygous it would fall in this category since the homozygous is different (non existent or very sickly) than the mutant phenotype seen in the heterozygous.

C. Dominant: Heterozygous and homozygous are both mutants and look the same. Example - it sounds like spider might fall into this category if someone proves a homozygous spider by breeding it to a large number of normals and producing only heterozygous spiders (see homozygous X heterozygous in rule number 4 above).

So, if you can remember the five rules of genotype inheritance and the phenotypes of the three mutation types you should be able to keep everything we have seen so far straight

Just to keep things interesting we might eventually discover mutations that are alleles (different mutations of the same gene) and mutations that are linked by being close together on the same chromosome. Both of these situations put a twist on the above rules when dealing with crosses between the related mutations (other wise you can figure using the above rules independently for each and accounting for random overlap between each independent outcome). Throw in a sex linked mutation (remember females are the ones with heterozygous sex genes in snakes) and we should have fun for years to come!

Ok, I need more sleep. I forgot the rule that I SHOULD have used for an example under C. Here is a corrected version (still probably a mistake or two left):

1. Normal X Normal = 100% normal
2. Heterozygous X Normal = 50% chance heterozygous, 50% chance normal
3. Heterozygous X Heterozygous = 25% chance homozygous, 50% chance heterozygous, 25% chance normal
4. Homozygous X Normal = 100% chance heterozygous
5. Homozygous X Heterozygous = 50% chance homozygous, 50% chance heterozygous
6. Homozygous X Homozygous = 100% homozygous

If you can remember those basic rules then all you need to do is remember the phenotypes for each mutant type and you can figure anything out. Here are the rules for the three types of mutations we have seen so far. We might eventually also see sex linked which gets really wild.

A. Recessive: Heterozygous is normal phenotype, only homozygous is mutant phenotype. Example - a heterozygous albino looks normal, only an animal with two albino genes (homozygous albino) looks albino.

B. Co-dominant (some say this should really be called “incompletely dominant” but regardless of which is more correct “co-dominant” is firmly established in the trade): Heterozygous is different from normal but homozygous is different yet. Example - a jungle pastel is a heterozygous super pastel (homozygous form).

Note: I think if we ever find a mutant gene that is fatal when homozygous it would fall in this category since the homozygous is different (non existent or very sickly) than the mutant phenotype seen in the heterozygous.

C. Dominant: Heterozygous and homozygous are both mutants and look the same. Example - it sounds like spider might fall into this category if someone proves a homozygous spider by breeding it to a large number of normals and producing only heterozygous spiders (see homozygous X normal in rule number 4 above).

Those six mating combinations are right on the money! They are worth memorizing, IMHO.

>B. Co-dominant (some say this should really be called “incompletely dominant” but regardless of which is more correct “co-dominant” is firmly established in the trade): Heterozygous is different from normal but homozygous is different yet. Example - a jungle pastel is a heterozygous super pastel (homozygous form).

As far as breeding results go, codominant and incomplete dominant mutants are identical.

I don't know enough about jungle pastel to be able to comment about them. But the tiger mutant in reticulated pythons fills the bill. A tiger reticulated python is the heterozygous form, and the super tiger retic is the homozygous form.

>Note: I think if we ever find a mutant gene that is fatal when homozygous it would fall in this category since the homozygous is different (non existent or very sickly) than the mutant phenotype seen in the heterozygous.

This is correct in some cases, like dominant yellow in the mouse. But many lethal mutants are recessive. The heterozygous individuals appear normal. I used to help breed a mutant like that -- jaundice in mice. Homozygous pinkies turned gold and died. The heterozygous individuals appeared normal. We had to keep test crossing unknowns to known heterozygotes and then keep the heterozygote x heterozygote matings to keep the stock going.

BTW, brindle in the black rat snake may be a sexlinked mutant. At least the males and females have different phenotypes. It may be a parallel to faded in pigeons, which is sexlinked.

And for real fun, try a sexlinked recessive semi-lethal.

Paul Hollander

SO in other words, if I bought a het albino python, he'd look like a regular python but with a very very small chance of breeding a real albino...

God that sucks, I want an albino bad but I can't afford $3,000 dollars on a snake.

if you bought a het albino bp it'll produce albinos year after year IF you pair him/her up with another het albino or albino.

The worst that could happen would be to buy 50% PH albinos and that's not bad at all considering that it's like flipping a coin on that gene. (TAILS NEVER FAILS HAHAHAHAHAHAHA). I can roll with those odds.

can you afford 1,000 or so to buy a pair of hets?

I can't even afford my car payment let alone the housing to breed snakes and two het albinos lol.

Actually, come to think of it, that wouldn't be a bad investment in the long run. Even though I would probably have albino's in like 5-6 years from now if I bought babyies, though im not sure at what age python's become sexually mature and ready to breed.

Hey. I've put together a page on my web site that describes the inheritance of simple recessive traits. I'm biased of course, but I think it does a nice job of explaining things. I welcome any and all feedback.....

Joe Pociask Pythons - Genetics