Some genetic questions

[LittleTreeGuy]

Let me start by saying, I in NO WAY mean to upset anyone or degrade anyone or their snake. You can't always show expression over forums, so pleas know, I am purely asking questions because I want to learn more, nothing else.

So, my questions revolve mainly around HETS. I understand this is a "non-visible" gene that the snake carries. I have only been into the snake scene a few months, and it's all revolved a lot around BP's. There is a lot to take in. I'm sure for those of you who have been doing it for years, you get tired of people like me. Sorry.

I guess my main question is, why would a HET or possible het cost more than a normal morph? A het pied for example, is there any chance of that animal producing a pied? I thought only visible pied x visible pied produced pied? If this is the case, why pay more for a snake that is possible het pied or het pied? Maybe pied is a bad example... like I said, i'm still learning. I've been playing around with the breeding generator tool on the world of ball pythons site and it's helped me a good bit, but the hets and their higher costs, from what I have seen, have me confused.

I guess in short, what is the relevance of a het animal? Does or can it actually produce another animal with it's het gene?

[blbsnakes]

Let me start by saying, I in NO WAY mean to upset anyone or degrade anyone or their snake. You can't always show expression over forums, so pleas know, I am purely asking questions because I want to learn more, nothing else.

So, my questions revolve mainly around HETS. I understand this is a "non-visible" gene that the snake carries. I have only been into the snake scene a few months, and it's all revolved a lot around BP's. There is a lot to take in. I'm sure for those of you who have been doing it for years, you get tired of people like me. Sorry.

I guess my main question is, why would a HET or possible het cost more than a normal morph? A het pied for example, is there any chance of that animal producing a pied? I thought only visible pied x visible pied produced pied? If this is the case, why pay more for a snake that is possible het pied or het pied? Maybe pied is a bad example... like I said, i'm still learning. I've been playing around with the breeding generator tool on the world of ball pythons site and it's helped me a good bit, but the hets and their higher costs, from what I have seen, have me confused.

I guess in short, what is the relevance of a het animal? Does or can it actually produce another animal with it's het gene?

Visual x visual will give you 100% visual offspring
Visual x het will give you 50% visual offspring on average
Het x het will give you 25% visual offspring on average.

So yes a het will produce a visual. That is why they are worth more.

[JoshSloane]

Hets carry the allele of interest in a recessive fashion. Meaning their DNA contains the coding sequence for the desirable trait, but it is not expressed phenotypically by that individual, because they only retain one copy. When that allele is passed onto offspring, and the offspring receive another of the same allele from the second parent, they will express the phenotypic trait.

To expand on what was stated above, each animal has chromosomes that exist in homologous pairs, meaning one set of chromosomes from mom, one set from dad. During meiosis, when gametes are created the homologous chromosomes split apart, to form a haploid cell. So statistically you have a 50% chance of passing on the DNA from mom and a 50% chance of passing on the DNA from dad. If the individual is heterozygous for a trait, this is why if bred to a normal there is a 50% chance of the offspring receiving the gene. And when you combine two hets to breed, they each have a 50% chance of passing on the trait, so their offspring will have a 25% chance of getting BOTH alleles from the parents (50%x50%)

[bproffer]

There was a discussion a week or so ago discussing possible het prices. The consensus seemed to be most people don't price possible hets any different than the normal (insert whatever gene here...), but some do. When it comes to possible hets, it is a crapshoot to see if they prove out. To some, that is worth the extra $100 or so gamble they are taking to produce a visual that would otherwise be much more expensive.

[Mr. Misha]

Check out this sticky for a crash course in genetics which will answer your question regarding hets vs possible hets.

http://ball-pythons.net/forums/showthread.php?t=52847



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[darkranger69]

possible het. are mostly sold as they are not carrying the gene except if it s a very new and expensive morph. honestly i won t pay for poss. het. except for sunset, white wash , atomic and maybe monarch and puzzle. Also the 2 main conditions will be a very trustable breeder; i will ask a lot around to know experience in different forum and the price been between 100 and 300 $ more depending on the morph.

[paulh]

....

So, my questions revolve mainly around HETS. I understand this is a "non-visible" gene that the snake carries. ....

That is only partly true.

Het is short for heterozygous. All gene pairs are either homozygous or heterozygous. By extension, a snake with a homozygous gene pair is homozygous, and a snake with a heterozygous gene pair is heterozygous. Please note that the following definitions say nothing about what the snake looks like. The definitions only specify the genes in a gene pair.

Definition of homozygous: a genetic condition where an individual inherits the same alleles for a particular gene from both parents. (http://ghr.nlm.nih.gov/glossary=homozygous)

A gene pair made up of two copies of the normal gene is homozygous. In this case the snake looks normal. Other homozygous gene pairs are made up of two copies of a dominant mutant (abnormal) gene, two copies of a recessive mutant gene, or two copies of a codominant mutant gene. In these cases, the snake does not look normal.

Definition of heterozygous: With respect to a particular trait or condition, an individual who has inherited two different alleles, usually one normal and the other abnormal, at a particular locus. (http://ghr.nlm.nih.gov/glossary=heterozygote)

A gene pair made up of a normal gene and a recessive mutant gene is heterozygous. In this case the heterozygous animal looks normal, and the hidden gene is the mutant gene. A gene pair made up of a normal gene and a dominant mutant gene is also heterozygous. The animal does not look normal because the normal gene is the hidden gene. A gene pair made up of a normal gene and a codominant mutant gene is also heterozygous. Again the animal does not look normal, but there is no hidden gene because both genes affect the snake's appearance. Even a gene pair made up of two differerent mutant genes is heterozygous. The snake does not look normal because there is no normal gene in the gene pair.

The reason for the belief that heterozygous snakes look normal is that for many years, all heterozygous snakes had a gene pair made up of a normal gene and a recessive mutant gene. But those days are over. Ball pythons with codominant mutant genes, like mojave and pastel, have been around for over a decade. Even dominant mutant genes, like pinstripe, are being discovered.

The value of a snake that is homozygous for a dominant mutant gene is that when mated to a normal, all the babies are heterozygous for that dominant mutant gene. When a snake that is heterozygous for a dominant mutant gene is mated to a normal, half of the babies are heterozygous for that dominant mutant gene. The rest of the babies are normals, which are worth much less.

Clear as mud?

[paulh]

Check out this sticky for a crash course in genetics which will answer your question regarding hets vs possible hets.

http://ball-pythons.net/forums/showthread.php?t=52847

Unfortunately, the pictures in that link are wrong. That is a pretty common mistake in herper genetics web pages.

I prefer the Genetics Home Reference, which can be freely downloaded. http://ghr.nlm.nih.gov/handbook

I just wish that when the GHR showed an X-shaped chromosome, they had made it clear that the chromosome is in the process of dividing into two rod-shaped chromosomes.

Here is a more accurate version (IMO) of the text in the "HOW DOES ALL THIS WORK?" section of http://ball-pythons.net/forums/showthread.php?t=52847:

HOW DOES ALL THIS WORK?

Picture a pair of shoestrings. Hold them up side-by-side. Now picture each shoestring run through colored balls, like a string of beads.

There are two chromosomes. Each string of beads represents the DNA strand in a single rod-shaped chromosome.

Each bead represents a single gene or allele.

A bead in one string and the corresponding bead in the other string represent a pair of genes/alleles located at a specific locus.

[Mr. Misha]

Unfortunately, the pictures in that link are wrong.

The pictures weren't meant to be scientifically accurate. It just an easy way of showing people who aren't familiar with genetics of how it works without confusing them.



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[paulh]

My preference is simple and reasonably accurate. The string of beads analogy is both. The pictures in the link are neither. Too bad.