Pinging BlackOak

[Sarah32306]

ping

I was wondering if you could explain to me the way that genes pass over from the parents to the foal, and if you could name the various color genes, that would be very helpful!

Also, what are some of the basic dilutions, and how do they appear?

You do not need to quote, I have replied turned on.


Thanks so much!!

[BlackOak2]

http://www.horseworldonline.net/forum/v ... 12&t=15900
That topic has a lot of the gene coding.
There are some there that are used ONLY on HWO, but a lot of them are actual gene coding that are used in the industry for horses.
Agouti is debatable. Depending on who you talk to, some will say there is only one agouti gene. Others work off of a theoretical two or three separate agouti sub-genes, that hasn't been proven wrong yet (at least in no studies we've been able to find). The agouti three-set, sub-gene theory, though not genetically located, has proven that there could be some fact to it, but how it appears to work when passed through the generations.
So be careful with the agouti. It's an interesting side-subject but could get you into trouble.

Now for how genes are passed from parent to foal.
The Punnett Square is the basic formula for how we define how genes are passed on from parents to foal. Each gene has two pairs and each of each pair, one is inherited from one parent and the other is inherited from the other parent.

This is NOT an example of horse genes, merely an example of gene passage from parents to offspring. However, this does explain how recessive and dominant genes are handled by passage and through usage by the body.
In this example, we see that one parent has blue eyes and the other parent has brown. Blue eyes are shown as recessive by the lower case 'b'... and brown as dominant by the upper case 'B'... this is generally the way all genes are handled, recessive being displayed as lower case and dominant as upper case.
The square itself is divided as a 1 in 4 offspring design, so we can easily determine how likely or unlikely a gene passage and expression can be. For our two parents, we can easily see that NONE of their children will ever express blue eyes, but Each One will be a blue eye carrier, which then tells us that with the right partner, THEIR children could be blue-eyed.
Do you need more info on that part?

Now we move on to dilutions.
In the game, our dilutions are defined as 'a color change to the base coat' and generally dilution describes as lightening and not darkening to the base coat. So all of our dilutions on HWO would include: Champagne, Cream, Pearl, Dun, Roan, Graying, Silver, Pangare.
Now there are a few explanations and exceptions to these dilutions. Roan CAN be considered a dilution. However, at it's base level it's not Exactly a dilute gene. Because it is white hairs intermixed with another color, it doesn't really fit in to the description as a dilution... however, because it's look makes it appear as a dilution, it is often referred to as a type of dilution. Also, the silver gene can be considered a dilute for manes and tails only, except when paired with the black gene, then it's a full-bodied dilute and the graying gene some may not consider a dilute at all, but a gene that makes hair a different color altogether and not just alters the original color itself.

Now we'll tackle each dilute, insofar as my own personal knowledge extends and only within HWO restrictions.
Champagne will always have freckles. Offers gold-coloration to chestnut and bay coats and a washed out brown, gray to blacks and browns. It's a dominant gene and two genes will not change appearance from one gene.
Cream is best described as an incomplete dominant. Incomplete meaning that when paired up with the same or in this case also, a different type of gene, it will change appearance. One only one cream gene is present, this gene will turn red colors toward a yellow hue or a tannish-yellow hue. But on black hairs, it's not strong enough to present itself. It's also not strong enough to change skin or eye color. However, when paired with a second cream gene, such a stronger combination turns red hairs almost to a very pale yellow or what I've referred to as a 'true cream' color. Black hairs are also diluted by the double cream and appear very washed out like a 'desert brown' or a dull, pale gold. The double cream also washes out manes and tails. They generally appear to be NOT white or silver and also NOT black or dark...but somewhere in between. And as a last influence, the double cream turns black skin pink and brown eyes blue.
Now for pearl. Pearl is recessive. It shares the same locus with cream... which means it's the same spot. We cannot have a double cream and a double pearl. We can only have a double cream, a cream and pearl or a double pearl... those are our only options. Double pearl can be easily mistake for double cream, except that pearl will not change the eye color.
Dun is what could be considered a 'true' dilution. This gene bleaches out whatever color it's on, either to a very mild degree, or a very extreme degree. Often times, dun will also leave behind stripes or certain patches of non-diluted hair. Dun is dominant.
Roan I already went over. Roan is also dominant.
The Graying gene I also went over, the little that needed to be said. Gray is also dominant.
Silver alters the base color of manes and tails toward the white spectrum. So it's not so much as a dilution gene as it is a polarizing gene (shifting toward the white spectrum ). Well, perhaps I'm incorrect on the words... It also does this on the black coat itself. Silver is also a dominant gene.
Pangare also called mealy. This is another 'true' dilution gene. This works the same way dun does, but attacks it at a different angle. And always 'comes up from the bottom'. Such as, pangare will express most from under the stomach (and the end of the nose, and around the eyes) and crawl upward from there. Pangare will affect the legs as well and can affect the entire body.

I think I've covered enough at the moment.

[Hazel!]

I just wanna add a few useful links. :D

This is a little game that lets you play around with genetic combos and see what it does to the horse's color.
http://www.jenniferhoffman.net/horse/ho ... 3000300000

And this is a calculator where you put in the sire and dam's color (and genetic info if you know it) and it'll give you a list of probabilities for the foal.
https://www.animalgenetics.us/Equine/CCalculator1.asp

[Sarah32306]

ping

This really helps alot! Thank you!

Is it possible to tell whether appearance genes are dominant or recessive? I mean besides color genes. Also, do you happen to know why when both parent have for example blue eyes, the child/foal (lol) has brown eyes? What I mean is, why when both parents have the same dominant gene, will the foal acquire a recessive gene?

ping

Thank you for the links those will help alot!

[Sarah32306]

ping

Also, what are Heterozygous and Homozygous genes?

[BlackOak2]

Heterozygous and homozygous are only another way of saying single gene or double gene.
Heterozygous has two different forms of the gene, as in: D/d - one dominant dun gene and not the other.
Homozygous is two of the same form of the gene, as in: D/D or d/d.

For our area, Hetro- means different while Homo- means same.

As for which appearance is dominant versus recessive... it's a little bit of thought calculation for this. If neither parent expresses a type of gene, but the foal suddenly has it, it can be assumed that the gene is recessive, a great example of this is the flaxen gene. However, if only one parent expresses a gene and the other parent does not, but the foal also expresses it, there is a chance that this is a dominant gene. But with this second example, one must remember the example of the blue eye, brown eye parents... the children are all carriers of a recessive blue eye gene and can throw blue-eyed offspring.
And this is generally how all genes work. The most basic form of any gene is either dominant or recessive. This is the basic way they work.

As for your question when both parents have blue eyes (assuming the blue is recessive) and the offspring have brown eyes (also assuming the brown is dominant), this would mean a couple different things have happened. The first and foremost assumption is that one of those parents (nominally the stud, because you can see the mare is pregnant), is NOT the father. Second, you're not looking at a recessive blue eyes on either or both of the parents (it's not blue-eye genes your working with, rather it's a different eye-gene altogether). Third, a mutation happened. Mutations can happen at any time and under MANY different circumstances. And fourth, a sleeping gene, in this case can also be called an 'ancient gene' was activated and changed the eye color because of some ancient gene instructions.
Those are, I think, the only reasons for something that should be true, in some cases is not true. With the sole exception of albino-ism. Which is the failure of a gene either to produce color or that it even has color to produce.

[Sarah32306]

As for your question when both parents have blue eyes (assuming the blue is recessive) and the offspring have brown eyes (also assuming the brown is dominant), this would mean a couple different things have happened. The first and foremost assumption is that one of those parents (nominally the stud, because you can see the mare is pregnant), is NOT the father. Second, you're not looking at a recessive blue eyes on either or both of the parents (it's not blue-eye genes your working with, rather it's a different eye-gene altogether). Third, a mutation happened. Mutations can happen at any time and under MANY different circumstances. And fourth, a sleeping gene, in this case can also be called an 'ancient gene' was activated and changed the eye color because of some ancient gene instructions.
Those are, I think, the only reasons for something that should be true, in some cases is not true. With the sole exception of albino-ism. Which is the failure of a gene either to produce color or that it even has color to produce.

Okay, thanks! Do you mind if I have a couple more questions?

I was wondering what some of the different eye conditions, colors, dilutions, etc. are in horses. I saw a post of your a while back about it, but didnt have time to really read it. I think you mentioned tiger's eye??

What are some examples of albinism in horses? Also, do you know when albinism is most likely to happen?

[Hazel!]

Wikipedia's telling me that true albinism (complete absence of any pigment, resulting in pink skin, pink eyes, and sight and hearing problems) has never been documented in horses--the gene mutation that causes albinism in other mammals has not been found in horses.

In horses, white is gonna be caused by (according to wiki)

1. Extreme dilution--pearl or cream gene
2. Max sabino
3. Max LP
4. Dominant white (on the KIT gene)(I don't think this exists in HWO)
5. Lethal white overo (homozygous O/O--overo doesn't exist in HWO, so we don't have to worry about lethal white)

I'm pretty sure that all 'white' horses on HWO are either extreme dilutes, or max tobiano (which never quite happens IRL)

[BlackOak2]

I'll keep answering your questions, insofar as my own knowledge extends... as long as you remember that I could be wrong.

Eye colors in horses is not my strong suit. I know that blue eyes can be linked to certain horse coat colors (like the cream gene), I THINK they are also in some cases linked to certain paint genes (overo comes to mind), but such things aren't yet a part of HWO. Right now, on HWO, we only have one separately standing eye-color gene. This is tiger eye. Named as such (in the real world) for it's similarity to a real tiger's eye color. They've also been called goat eyes, for the same reason.
Tiger eye genes in horses, is directly related to the champagne gene and in real life is generally ONLY associated with the Paso horses.
The tiger eye gene is likely best described as an incomplete recessive. What this means is that when paired with certain other genes, it can express. In this case, on HWO, that singular 'other gene' is champagne. Only when paired with the champagne gene, can a SINGLE tiger eye express itself. Like paving the way for the gene to be seen. Otherwise, this gene remains hidden unless TWO copies are carried. Also, a single tiger eye gene, when expressed, will look differently then two genes (in this case, this is working a bit like the cream gene). The tiger eye gene is green-hued always, either as a hazel or gray-green or bright, brilliant emerald green or a stormy-green. The hazel hue is generally seen as a single gene, while the brighter, more brilliant greens are found only when two tiger eye genes are together.
That's about as far as I know eye colors in horses. Of course, I'm not getting into the diseases and illnesses of eyes, that's a 25-book-set encyclopedia style answer there!

So, depending on who you talk to, it is generally believed that albino-ism simply cannot exist in horses. I am not one of them. As the definition of albino is the inability or failure of a gene to produce color, in my belief, albino-ism in horses IS a possibility, but because of the very nature of it (a failing gene) and our general breeding practices, such a horse is simply 'discouraged' to exist. There have been some cases in the real world of 'possible' albino horses, most of them proven to be simply white or types of light-based colors. But there have been others that show all the signs of being albino, but because of certain circumstances, were not genetically tested. So, just because it hasn't yet been proven to exist, doesn't mean it CAN'T exist.
In other animals, albino-ism generally and most often happens as a deficient mutation as a fetus. The genes, for whatever reason, simply lack the ability to produce color, therefore we are offered a 'full-body' albino. However, we have successfully bred animals to be only partially albino, as in the case of the new zealands... also looking up himalayan lilacs bring up a few.
Albino-sim is marked most often by red-eyes and pale skin with white hair or fur. Generally speaking, albino is carried throughout a lifetime (but there are cases of it popping up and disappearing, depending on the gene's controlling it, they'll switch on and off randomly, the 'off' position is the failure of color production).

[BlackOak2]

And Hazel! is correct, insofar that all 'white' horses on HWO at this point are only pseudo's... the white genes for white coat color has not yet been introduced on HWO.