Reptile & Amphibian Forums

Hello all,

I have been wondering and thinking about a particular question dealing with genetics, particularly simple recessive genes. Anyways, has anyone ever thought about the possibility that there is a simple recessive gene out there that somewhat operates like a dominate gene. For example, you breed a ball that is 100% het. for whatever to a completely normal ball python. What if all the babies turned out to be hets. every time. I am not talking about Pastels or Mojave, I am talking about a trait that isn't seen (simple recessive) being passed on to its offspring every single time. Is that possible? I think it could be but we have not seen it yet? That would not be suprising because all the babies would look normal and be called 50% het for that particular gene. Anyways, there is my thought of the day and my rant. Post any comments and replies

HOOPY

That's pretty much impossible due to the physical nature of chromosomes. It's a long explanation, but I can go into it. Of course, it's possible that in any given clutch that would happen, but statistically it shouldn't.

For ever gene there are 2 alleles. Each parent gives one of these alleles in its gametes (egg and sperm) to the formation of a zygote (embryo/baby snake). If one parent is 100% het for something, it has the genotype "Aa". Therefore it can ALWAYS give an "A" or an "a". ALWAYS. Without fail.

If you define an allele as any of the alternative forms of a gene that may occur at a given locus, then there can be more then 2 alleles. For instance in human blood type. you can have A, B or O blood types. Both A and B types are dominant and O is recessive. Which gives us 4 different blood types. If the alleles are AA (the homozygous form) or AO (the heterozygous form) you have blood type A. If they are BB or BO you have blood type B, if they are AB you of course have blood type AB and if you have OO you have blood type O I'm not aware of multiple alleles being discovered yet in ball pythons, but it's certainly a possibility.

Mark

>>For ever gene there are 2 alleles. Each parent gives one of these alleles in its gametes (egg and sperm) to the formation of a zygote (embryo/baby snake). If one parent is 100% het for something, it has the genotype "Aa". Therefore it can ALWAYS give an "A" or an "a". ALWAYS. Without fail.

I meant that any parent ONLY carries 2 possible alleles for each gene, therefore they can ONLY pass on one of those in their gametes. There could be a million different alleles for a gene, but the animal will only have 2 (according to Mendel genetics).

didn't understand what you meant. now I do.

Mark

I don't even understand what I mean most of the time, LOL!!

Guys, the place where an allele is supposed to be found on a chromasome is called a locus, plural would be loci. So there are two alleles that may or may not be the same at corresponding loci. I hope that helps clarify things.

However, there are also different loci that code for the same thing. Take for example, skin and eye color in humans. I'm not aware of any in reptiles, but the chances that there are multiple loci coding for the same thing is pretty high. -Whit

I'm unclear as to what you mean by 100% and 50% het.

If an animal has the recessive gene on both chromosomes - say for blonde hair and blue eyes or albino ball pythons - that animal isn't het anymore, its homozygous.

but meretseger is correct, its impossible for something to be het and only 50% het. -Whit

theres a 50% chance of it being a het.. this comes from breeding a het(Aa) to a normal(AA)... you get (theoreticly) 50% normals (AA) and 50% hets (Aa).... all the offspring look normal.. but you have a 50% chance of getting one thats a het.. the only way to know is to breed it... am i right about all this? dave
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"i have a mortal wound!"
"where? where does it hurt?"
"oh, pretty much around the big bloody spot"
"come inside. ill get the neosporin. da na na na na - NEO! ba na na na na na na - SPORIN! blee nee nee......."

if he meant % POSSIBILITY of being het, sure, but that's not how I took it.

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Quotes : For example, you breed a ball that is 100% het. for whatever to a completely normal ball python. What if all the babies turned out to be hets. every time

That would not be suprising because all the babies would look normal and be called 50% het for that particular gene
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Now by 100% het, did hoopy mean (aa) or (Aa)? that would be the question because if you cross (aa) - recessive homozygous - to (AA) - normal homozygous, all the offspring would be (Aa)

However, if you cross (Aa) - recessive het - to (AA) - normal homozygous, in theory: 50% of the offspring is (AA), 50% of the offspring is (Aa)

There is NO way that when you cross a recessive het to a normal homozygous that all the offspring could be hets as Hoopy proposes, unless there was a trisomy (3 corresponding chromosomes instead of just the pair). Trisomies are often deadly, and if the embryo survives to infancy, the chances of it surviving to adulthood are slim. There are of course always exceptions, but trisomy individuals are often sterile. Anyway, that's genetics 101. -Whit