# Genetics Confuses Me !!!



## deefa139 (Mar 9, 2008)

Am trying to get my head around simple genetics and have started reading posts on here and elsewhere but it is as clear as mud at the moment.

Am I right in thinking :

Normal Male/Albino Female = Het Albino Off Spring
Albino Male/Albino Female = Albino Offspring


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## SpiritSerpents (Mar 20, 2011)

You are correct.


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## snakekeeperteznemz (Dec 20, 2009)

recessive genes are pretty simple to predict.
if u have one visual and one non, like u said u get hets. if u need a visual to a het u get half visual, half hets. two visuals make more visual babies
simply pair up visual genes to get more of the same.

Tez


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## Spider Call (Mar 23, 2007)

This is where the line is being stepped on. 

Albino x albino doesn't always = albino. They need to be the same strain of albino, or they will still be normal het for both strains.


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## Zerox Z21 (Oct 10, 2012)

I'm not versed in leopard geckos (assuming they are the subject) so am not sure how 'het' works with albinism but I can give a basic run down of general genetics for you.

Assuming we have one albino strain and one normal strain, genes can be written as such:
A=Normal
a=Albino
Albino is the recessive form of the gene so is a small a, and overridden by A.
So animals with AA or Aa (aA is written as Aa) express 'normal' as the phenotype, even though they can have some albino genes.
So the only way to have an albino is to have aa, since there is no A to override the recessive a.
So for guaranteed albino young you need two aa parents. You can also have, say Aa and aa parents, in which case you will get a 50/50 ratio of normal/albino young, since one parent has Aa and 50% of the time it will pass on the A.
This is a very simple example but I hope it explains the concept.

In reality an example is ginger haired people. The gene for red hair is recessive which is why it is rarer. Same applies to blond hair. A brown or black haired person, if they have two black/brown genes (like AA), then even if they have a ginger partner, the children will always have brown/black hair, hence why such pale hair colours are rarer in society.

As for multiple albino strains, the difference here is like the difference between genes for black or brown hair, even though the results look similar, if it's a different gene you may as well be looking at the Aa example again; chances are that one albino strain will be dominant. If neither is dominant, you can get an animal that expresses a mixed phenotype e.g. grey and brown furs are equally dominant in mice, so one with a mix of grey and brown genes will have a mix of grey and brown hairs.
I suppose this is true of humans; mixed race children, for the most part, are right in between the shades of skin tone of their parents; darker than one, paler than the other.


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## paulh (Sep 19, 2007)

There is a reason why genetics is so confusing. Too many people are passing on incorrect information. A newbie cannot tell what is good and what is not. There is good information in the genetics 101 sticky in this forum. There is also good information in the genetics tutorial at Serpwidgets - Home

This is correct:


Zerox Z21 said:


> I'm not versed in leopard geckos (assuming they are the subject) so am not sure how 'het' works with albinism but I can give a basic run down of general genetics for you.
> 
> Assuming we have one albino strain and one normal strain, genes can be written as such:
> A=Normal
> ...


The following quote is riddled with incorrect information. 



Zerox Z21 said:


> In reality an example is ginger haired people. The gene for red hair is recessive which is why it is rarer. Same applies to blond hair. A brown or black haired person, if they have two black/brown genes (like AA), then even if they have a ginger partner, the children will always have brown/black hair, hence why such pale hair colours are rarer in society.
> 
> As for multiple albino strains, the difference here is like the difference between genes for black or brown hair, even though the results look similar, if it's a different gene you may as well be looking at the Aa example again; chances are that one albino strain will be dominant. If neither is dominant, you can get an animal that expresses a mixed phenotype e.g. grey and brown furs are equally dominant in mice, so one with a mix of grey and brown genes will have a mix of grey and brown hairs.
> I suppose this is true of humans; mixed race children, for the most part, are right in between the shades of skin tone of their parents; darker than one, paler than the other.


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## deefa139 (Mar 9, 2008)

Zerox Z21 said:


> I'm not versed in leopard geckos (assuming they are the subject) so am not sure how 'het' works with albinism but I can give a basic run down of general genetics for you.
> 
> Assuming we have one albino strain and one normal strain, genes can be written as such:
> A=Normal
> ...



This I got, thanks the rest just confused it more but thanks all for the replies.


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## Zerox Z21 (Oct 10, 2012)

paulh said:


> There is a reason why genetics is so confusing. Too many people are passing on incorrect information. A newbie cannot tell what is good and what is not. There is good information in the genetics 101 sticky in this forum. There is also good information in the genetics tutorial at Serpwidgets - Home
> 
> This is correct:
> 
> ...


Sorry =[ What's wrong with it in particular? I know I've likely assumed certain things without really clarifying it. Also looking back I have worded it pretty badly.

I do remember there are such things as co-dominant genes, and an example we learned was something to do with mixed fur colours. Think if black and white hair is co-dominant, you'd get an animal that looks grey I guess, but the hairs would be black and white.

I think the rest is stuff I've assumed from what I know =/


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## paulh (Sep 19, 2007)

Zerox Z21 said:


> Sorry =[ What's wrong with it in particular?


Human genetics does not make very good examples. Skin color involves three gene pairs at the very least. I don't know how many gene pairs affect hair color, but it is more than one. Trying to explain multiple gene pairs in terms of one gene pair is confusing at the very least. And humans have not had a standard designated. Mice, on the other hand, have had wild type designated as normal, or the standard. It is pretty easy to designate the wild type as standard in most herps, too.

If you are going to use an animal example, please specify the species. Because two different species may have mutant genes with similar names but different inheritance. Hypomelanistic (hypo) is a dominant mutant gene in boa constrictors but a recessive mutant gene in corn snakes.

Or the same species may have two different genes with similar names and inheritance that are genetically unrelated. Boa constrictors, for example, have two recessive mutants (Kahl albino and Sharp albino). Crossing a Kahl albino to a Sharp albino produces a snake that has two gene pairs of interest. One gene pair has a normal gene paired with a Kahl albino gene. The second gene pair has a normal gene paired with a Sharp albino gene. And the snake looks normal instead of like either albino. That's what Spider Call meant earlier in this thread.

The brown mutant gene in mice is recessive to the normal (gray?) gene.


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## Zerox Z21 (Oct 10, 2012)

paulh said:


> Human genetics does not make very good examples. Skin color involves three gene pairs at the very least. I don't know how many gene pairs affect hair color, but it is more than one. Trying to explain multiple gene pairs in terms of one gene pair is confusing at the very least. And humans have not had a standard designated. Mice, on the other hand, have had wild type designated as normal, or the standard. It is pretty easy to designate the wild type as standard in most herps, too.
> 
> If you are going to use an animal example, please specify the species. Because two different species may have mutant genes with similar names but different inheritance. Hypomelanistic (hypo) is a dominant mutant gene in boa constrictors but a recessive mutant gene in corn snakes.
> 
> ...


You clearly know more than me, I was (at least the first part that made sense!) just repeating what I'd learned at A level Biology.
I did figure that humans were more complicated than that but thought that, were it the case, it might be a good example of how co-dominance creates a phenotype that is representative of both genes. I suppose in retrospect that was foolish. The fur example I was thinking of was, in the textbook we had, referring to rabbits. I think it's a mix of brown and grey and the result had a particular name I forget.
It did use the hair colours as examples though, so at least I know blonde/ginger should be recessive. I think they're linked to eye colour somehow too, so not sure how that works entirely.
Really I was just trying to use vague examples to demonstrate my point, but didn't necessarily intend accuracy. Which is stupid. At the very least I ought to have been clear about how I'm using the example (e.g. assuming human skin colour is controlled by one gene it may be blah blah blah).

And I...vaguely figured the albino thing was like that, just different genes that have a similar effect. So a true, say, Sharp albino would have both gene pairs having a normal and Sharp gene, which results in Sharp albinism?

I feel rather foolish now, I do apologise


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## bothrops (Jan 7, 2007)

Zerox Z21 said:


> You clearly know more than me, I was (at least the first part that made sense!) just repeating what I'd learned at A level Biology.
> I did figure that humans were more complicated than that but thought that, were it the case, it might be a good example of how co-dominance creates a phenotype that is representative of both genes. I suppose in retrospect that was foolish. The fur example I was thinking of was, in the textbook we had, referring to rabbits. I think it's a mix of brown and grey and the result had a particular name I forget.
> It did use the hair colours as examples though, so at least I know blonde/ginger should be recessive. I think they're linked to eye colour somehow too, so not sure how that works entirely.
> Really I was just trying to use vague examples to demonstrate my point, but didn't necessarily intend accuracy. Which is stupid. At the very least I ought to have been clear about how I'm using the example (e.g. assuming human skin colour is controlled by one gene it may be blah blah blah).
> ...




I think you may have either forgotten a few of the details from the A levels, forgot to put them in, or didn't quite 'get' it when you did learn it. :whistling2:

The rabbit example you refer to is the multiple alleles at a single locus example involving four alleles that produce four phenotypes (wild type (agouti), grey (chinchilla), white body with black ears, legs and nose (Himalayan) and white with red eyes (albino)).
The agouti allele is dominant to all of the other three, the albino allele is recessive to the others. Chinchilla is dominant to Himalayan.

There is no co-dominance in this multiple allele example. 


An example of codominance frequently used in the A level text books is the snap dragon flower where red and white flowers, when bred together produce pink flowers said to demonstrate 'codominance'. However, this is technically incomplete or partial dominance (i.e. the red does not completely dominant the white or vice versa). They would have to have produced red and white spotted flowers to show true codominance (both alleles expressed in the heterozygous phenotype).






In the case of your last sentence, the Sharp and Kahl alleles sit on different loci. So rather than "a true, say, Sharp albino would have both gene pairs having a normal and Sharp gene, which results in Sharp albinism" instead, a Sharp albino has two copies of the Sharp allele at the Sharp locus and two normal alleles at the Kahl locus. A Kahl albino has two Kahl alleles at the Kahl locus and two normal alleles at the Sharp locus.


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## Zerox Z21 (Oct 10, 2012)

bothrops said:


> I think you may have either forgotten a few of the details from the A levels, forgot to put them in, or didn't quite 'get' it when you did learn it. :whistling2:
> 
> The rabbit example you refer to is the multiple alleles at a single locus example involving four alleles that produce four phenotypes (wild type (agouti), grey (chinchilla), white body with black ears, legs and nose (Himalayan) and white with red eyes (albino)).
> The agouti allele is dominant to all of the other three, the albino allele is recessive to the others. Chinchilla is dominant to Himalayan.
> ...


I think my problem is fuzzy memory! Agouti was the word I was thinking of. I do remember those other colours being mentioned as well. It has been a while.

Nothing on snapdragons ever came up. If true codominjance is production of separate red and white flowers, what sort of result might we expect in an animal (for example codominant fur or skin colours...assuming that exists). Now that I think about it, what I may have meant was partial dominance.

Thanks for rectifying me on the albinism, that makes sense. It also means that they can never produce an albino together as they always donate one gene each from each locus, one of which will always be normal assuming the gene examples you mentioned.
If it's possible (though convoluted) to obtain a snake with two Kahl genes AND two Sharp genes, would we expect anything interesting at all or would it just look pretty much the same?

Thanks for your patience!


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## bothrops (Jan 7, 2007)

Zerox Z21 said:


> If it's possible (though convoluted) to obtain a snake with two Kahl genes AND two Sharp genes, would we expect anything interesting at all or would it just look pretty much the same?
> 
> Thanks for your patience!


 
Your welcome - though no patience is needed - consider this a free revision/refresher class!

I've asked on various forums if a double homozygous Kahl and Sharp animal exists and never had a definitive answer.

The two mutations must have been mixed initially in order for us to know they are not compatable. Also, the double hets produced by breeding a visual Kahl to a visual sharp would almost certainly have been bred back to each other to find out what was happening when the intial breeder (assumedly Peter Sharp) was trying to work out whether he truely did have a new strain of albinoism. With a 1/16 chance of a double homozygous Kahl/Sharp boa, I would be surprised if one wasn't produced (though pulling it out from the Sharp het Kahls and Kahls het Sharps also in the litter may have been tricky!)

I have yet to hear anything definitive on the results of those crossings or the wherabouts of those animals today.


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## paulh (Sep 19, 2007)

My understanding is that Brian Sharp crossed a Kahl albino with a heterozygous Sharp albino. (Or the other way around??? Can't remember for sure.) All the babies were normals. If the two albino genes could make a gene pair, the expectation is that half the babies would not be normal. My understanding is that he stopped there.

I have not heard of any snakes that were both Kahl and Sharp albinos, too. I can't tell the difference between the two albinos, at least in pictures. Generalizing from work done in other species, I most likely could not tell the difference between the two types of albinos and the combination.

Incomplete dominance: A snapdragon with two red genes has red flowers. A snapdragon with two white genes has red flowers. A snapdragon with a red and a white gene has pink flowers, which are intermediate between the red and white flowers. Only the red gene produces pigment but cannot make up for the white gene's null performance. 

An example of codominance is in Burmese, Siamese, and Tonkinese colored cats. The Burmese gene produces melanin. The Siamese gene produces less melanin than the Burmese gene. A cat with a Burmese gene paired with a Siamese gene has Tonkinese coloration, which is intermediate between Burmese and Siamese coloration. Both genes contribute to the coloration. The mixture is inside each pigment cell so the result looks intermediate to the human eye.

The important thing to remember is that with both codominant and incomplete dominant genes, you can tell what genes are present by looking at the animal or doing a simple test. You can't do that all the time with dominant and recessive genes.

Different text books use different numbers of terms and different definitions for codominant and incomplete dominant genes. Most of the other terms are more or less synonymous with one of those two. All this is confusing and pretty much irrelevant to a breeder. The simplest solution is to lump them all together under a single term. "Codominant" has fewer letters to type than any of the other dozen or more available terms so is the term of choice. The professional mouse geneticists have done the lumping, but their preferred term is "semidominant". C'est la vie.


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## Zerox Z21 (Oct 10, 2012)

Genetics are fun aren't they?

I was curious about the Kahl/Sharp thing because I wasn't aware albinism could be derived from more than one gene. I figured it was a similar/same gene in many animals since albinism is typically a lack of pigmentation. Either that or mutated failed gene pairs that obviously don't function and end up with no pigment. I assume if albinism is like that, then a Kahl/Sharp double paired snake would simply look the same as the result is the same; no pigmentation. But the fact there's more than one way to that end made me curious.


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## paulh (Sep 19, 2007)

A single gene does not produce the finished product. It is more like a biochemical assembly line. Each gene pair is the equivalent of a station in the assembly line. Gene pair #1 does something to the raw material. Gene pair #2 does something to what leaves gene pair #1. Gene pair #3 does something else. And so on until the finished product rolls off the assembly line. We herpers are looking at flaws in the finished product and trying to figure out how many stations there are in the assembly line and whether only one or more than one is malfunctioning.Molecular biology looks at the machines and tries to figure out where they fit in the assembly line, what they do, and how they are controlled. My hat is off to the molecular biologists, because I think their job is much more difficult than anything we herpers do.

By the way, there are three unrelated albino mutant genes in leopard geckos.


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## Zerox Z21 (Oct 10, 2012)

paulh said:


> A single gene does not produce the finished product. It is more like a biochemical assembly line. Each gene pair is the equivalent of a station in the assembly line. Gene pair #1 does something to the raw material. Gene pair #2 does something to what leaves gene pair #1. Gene pair #3 does something else. And so on until the finished product rolls off the assembly line. We herpers are looking at flaws in the finished product and trying to figure out how many stations there are in the assembly line and whether only one or more than one is malfunctioning.Molecular biology looks at the machines and tries to figure out where they fit in the assembly line, what they do, and how they are controlled. My hat is off to the molecular biologists, because I think their job is much more difficult than anything we herpers do.
> 
> By the way, there are three unrelated albino mutant genes in leopard geckos.


Cool about the leopards. Wonder how many more can be found! Suppose this might explain all the morphs partly too...could be wrong though. I just see that there's ALOT of specific morphs. Prefer wild types myself of any species.
And I know the way I said it wasn't clear, but I'm aware that a single gene pair alone is not the sole controller of any aspect of an organism (I really hope that doesn't sound arrogant...). I just find it interesting that two particular variants of different genes can have the same result. It's possibly likely that they may be near each other in the DNA strand (i.e. they're both in the part that codes for pigmentation).

I do imagine thorough investigation is difficult. When any single factor such as pigmentation can be controlled by a code that can be tens or even hundreds of base pairs long...eugh.


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