A (lengthy) article on BP Gentics

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Originally Posted by Dread

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Originally Posted by Dread

"We are already aware that chromosomes come in pairs, and as such, so do genes."
-Are we aware of this already?
-Also, if you think alleles only come in pairs, there is a significant limitation in your knowledge that if addressed will help with the short-comings of the genetic information presented here.

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Are you talking of hemizygous loci like the X and the Y chromosome. OR the Z and W in birds and reptiles? Because pythons are ancestrally primitive snakes they don't have much differentiation between their sex chromosomes so I think it’s fair to say that most of their genes come in pairs.

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Originally Posted by Dread

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Originally Posted by Dread

"A recessive allele, causes a phenotype that is only visible in the homozygous form. An Albino, for example, is a simple recessive trait."
-Traits are recessive, meaning the allele in question does not have a visible effect unless the 'normal' allele's influence is removed. You'll want to careful when using the term "recessive allele" though this is probably more of a pet peeve.
-generally, "An Albino" would refer to an amelanistic individual, not a trait.

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Your being a little "nit-picky" here, Dread.

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Originally Posted by Dread

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Originally Posted by Dread

"A dominant allele, causes a phenotype that is visible in both the heterozygous and homozygous form."
-this definition does not distinguish between dominant and co-dominant. Since you're so intent on using your own definitions for things, incorporate the fact that the homozygous and heterozygous forms are visibly indistinct.

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Again you’re being a little nit-picky here. Overall, the section titled "Types of genes" is pretty good in my opinion.

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Originally Posted by Dread

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Originally Posted by Dread
Coloration of the Punnett Square is quite impossible with "paper and pencil", and needless.

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Coloration is great for educational purposes. I like it.

I do not like the use of the letter N or n for normal. I like to stick with the same letters when talking about alleles of the same gene. This way you know that A and a are alleles of the same gene C and c are alleles of the same gene. You also know something about dominance relationship between the two alleles. You know that C is dominant to c. It may be complete or partial dominance but you know that C is dominant to c somehow.

This is somewhat a matter of preference as different geneticists use different notational systems. For example, Fruit fly (Drosophila) geneticists use a one or two letter symbol system, with a "+" sign. The "+" sign is used to designate the normal or wild-type phenotype.

For example, vg+vg+ would be a normal, vg+vg would be a wild-type, and vg vg would be the phenotypic expression of a recessive mutation. This is real trait by the way-->vg codes for "vestigal" or shortened wings.

Your notational system could work as long as you designate capital "N" and lower-case "n" as alleles of any gene that code for wild-type phenotypes. N could not ever be used to designate a mutant morph. Little n would be used in cases where the mutation coding for the genetic morph is dominant or co-dominant with the wild-type or normal allele.

Notational systems are very specific to the model organism in biology. I see no reason in principle why ball python breeders or reptile hobbyists can not come up with their own variation--as long as it's internally consistent. Though I'm also a fan of using what's not broken!

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Originally Posted by Dread

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Originally Posted by Dread


"However, where these chromosomes can differ [is] in the alleles they carry."
-Most spell checkers will detect sentence fragments....
-Also, chromosomes may also differ because of imprinting, meaning the chromosome from the mother can behave differently than the same chromosome from the father.

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Again you’re being picky again. Though sometimes I can be too picky as well.



But you’re also not being really technically correct according to our best knowledge. Genomic imprinting is known at this time to occur only in mammals. For those of you who don't know, genomic imprinting, or simply imprinting, is the phenomenon where the behavior or expression of a gene depends on the parent of origin. In other words, you can inherit the same piece of DNA from your mom and the same piece of DNA from your dad, but the maternal allele acts differently than the paternal allele. It is called imprinting because the parent leaves a sex-specific imprint or mark on the allele that is transmitted to the offspring. This sex-specific mark is in the form of a chemical modification to DNA, called cytosine methylation. I use to work in a genomic imprinting lab and have a peer-reviewed paper on it in Molecular and Cellular Biology.

Incidentally, I believe that genomic imprinting is unlikely to be found in reptiles. There have been no documented cases of natural parthenogenesis in mammals. The reason behind this is that many mammalian genes and chromosomal segments undergo genomic imprinting. Basically, a mammalian offspring can not be produced when both sets of chromosomes come from the same parent because all loci that are imprinted would have abnormal levels of gene expression.

Now parthenogenesis has been found in many reptiles, the most recent being the Komodo dragon. The occurrence of natural parthenogenesis suggests that imprinting is not a major factor for reptiles. This is because an offspring can be produced from only the female's germ line. This suggests to me that imprinting isn't at work, because viable offspring don't require imprints from the male germ line.

Imprinting is more of a matter of epigenetics than genetics so I would not worry too much about it in an article of ball python genetics.

He may be being nitpicky but for the average joe who knows nothing about ball python genetics this article can be confusing.

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Originally Posted by tmlowe5704

He may be being nitpicky but for the average joe who knows nothing about ball python genetics this article can be confusing.

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And your not being very helpful.

JHall keep working on it.....it will get there.

wow great open source best thing ive read on genetics besides the genetics book i own

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Originally Posted by tmlowe5704

He may be being nitpicky but for the average joe who knows nothing about ball python genetics this article can be confusing.

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Given the fact that there are litterally hundreds of threads between all of the reptile forums that start "What will I get when I cross a..." there isn't exactly a superior resource available for the average Joe anyway.

Fortunately, this forum has at least 2 people with an extrodinary amount of knowledge when it comes to genetics, and hopefully after implementing their suggestions this article will be that much closer to clearing up confusion.

I truly appreciate constructive criticisms thus far, but your comment certainly wasn't constructive. If you would like to point out areas that you feel are incorrect, or could be better, feel free to do so.

Well I've made most of the suggested corrections by Dread and Mendel, and I think it gives the article a little more professional appearance. Although, it still definately needs some work.

Some areas that I didn't make the suggested changes:

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-For this to be a truly informative and useful article, you will probably want to investigate the different types of pigment produced by the wild-type, and discuss whether it is a disrupted gene, a disrupted promoter, or an upstream/downstream component of a genetic system that leads to phenotypic expression.

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I didn't add this information, mostly due to the fact that it does seem readily available. However, I'm not sure that the article itself would benefit from going into that much detail, especially since I'm only using a single example. Perhaps that would be something to go into detail in the respective morph pages, that way each morph has it's own detailed explanation, instead of just hitting on Amelanistics.

I did make the changes to the Punnett Squares as suggested, however, I think my explanation on why simple recessive notation differes from codominant and dominant notation is weak and confusing, and probably needs a serious rewrite. I'm thinking a Punnett Square example with a codominant morph would be more appropriate.

I did, however, leave the colorization intact. I agree with Mendel on this one. The purpose of the article is education, and the examples are intended to show how the individual squares are filled in. By showing the concept with color, I think it will be easier to understand when using pen and paper.

Thanks again for all of the suggestions, they certainly helped in making some really confusing aspects of the article a little more straight-forward, but there is still much to be done :).

"Recessive, codominant and dominant morphs are often referred to as base mutations. This is understood to mean morphs that exist in the wild. Complex types, like the double recessive mutation, is called a designer mutation, in other words, it's highly unlikely that this mutation will occur in the wild."

This needs some work.

Define the concept of a genetic morph.

Then Differentiate between base and designer morph. Designer mutation is rather misleading because most designer morphs have mutations in two separate genes.

Designer mutations make it sound as though the breeder is using mutagenesis to induce mutations in the animal.

See number 8 on this page.

I also think it would be helpful to include a link on these pages to this site.

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Originally Posted by jhall1468

I truly appreciate constructive criticisms thus far, but your comment certainly wasn't constructive. If you would like to point out areas that you feel are incorrect, or could be better, feel free to do so.

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I did not see my post as being offensive or whatever. By Mendel saying dread was being nitpicky, I was just backing up dread saying for the average joe who wants to learn about BP genetics, this could be an excellent resource if you "dumb" it down a bit for someone starting out interest in BP genetics. I know there will never be a best source for genetics info, but I feel this one has the possibility to be one of the best.

a note here for clarity. i just edited mendel's post #11

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Originally Posted by tmlowe5704

I did not see my post as being offensive or whatever. By Mendel saying dread was being nitpicky, I was just backing up dread saying for the average joe who wants to learn about BP genetics, this could be an excellent resource if you "dumb" it down a bit for someone starting out interest in BP genetics. I know there will never be a best source for genetics info, but I feel this one has the possibility to be one of the best.

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I didn't think you were being offensive. I just didn't think you being being helpful...big difference.

As far as backing Dread up...my point was that by Dread being nit picky he wasn't "dumbing it down". Reread my reponses to Dread and I think you'll see what I mean-no need to mention things like imprinting or hemizygous loci in a beginner article. They are too technical.