# Please explain everything to me.....



## cobalobM (20 June 2013)

Re colouring.

was reading about all the genes etc but its all very confusing but I did find it extremely interesting! so, anyone want to help me?! and where did you all learn everything?! 

okay so homozygous has 2 of the same genes, heterozygous has 2 different (is that right?!)
if a horse has 2 grey gene's then it will defo grey out? (but how does it get the other colouring when it is born??
if a horse has 1 grey gene then there will be 50% chance it will grey out? 


and anyone have any links where i can learn/read some more?! its very complicated!!


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## Dogrose (20 June 2013)

horselessb said:



			okay so homozygous has 2 of the same genes, heterozygous has 2 different (is that right?!)
		
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Yes, homozygous means both of a pair of genes are the same, whether they are a mutated version or a normal version. Heterozygous means they are different, usually one normal and one mutation but there are some genes which have multiple mutations.




			if a horse has 2 grey gene's then it will defo grey out? (but how does it get the other colouring when it is born??
		
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The grey gene is there in addition to any other colour the horse may have, a horse can be any colour and with any markings and have the grey gene too as it is in a different place on a chromosome than the genes which cause other colours. A horse that will grey out is nearly always born with dark rich adult colouring (e.g. very black legs on bay), not the usual pale foal colour, except for the silver dapple gene which causes rapid greying and the foals can be born nearly white already. The grey gene causes the colour producing cells at the base of the hair to produce excessive pigment then causes them to stop working so the hairs gradually begin to grow without the original colour.
Technically I suppose the grey gene is actually a defect not a colour.



			if a horse has 1 grey gene then there will be 50% chance it will grey out? 

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No, grey is a dominant gene, if a horse has one or two copies of the grey gene it will still grey out. If a horse has only one copy of grey (heterozygous) it will pass that gene on to its offspring 50% of the time.


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## cobalobM (20 June 2013)

Dogrose said:



			Yes, homozygous means both of a pair of genes are the same, whether they are a mutated version or a normal version. Heterozygous means they are different, usually one normal and one mutation but there are some genes which have multiple mutations.



The grey gene is there in addition to any other colour the horse may have, a horse can be any colour and with any markings and have the grey gene too as it is in a different place on a chromosome than the genes which cause other colours. A horse that will grey out is nearly always born with dark rich adult colouring (e.g. very black legs on bay), not the usual pale foal colour, except for the silver dapple gene which causes rapid greying and the foals can be born nearly white already. The grey gene causes the colour producing cells at the base of the hair to produce excessive pigment then causes them to stop working so the hairs gradually begin to grow without the original colour.
Technically I suppose the grey gene is actually a defect not a colour.


No, grey is a dominant gene, if a horse has one or two copies of the grey gene it will still grey out. If a horse has only one copy of grey (heterozygous) it will pass that gene on to its offspring 50% of the time.
		
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Numpty question- whats a mutated version and a normal version?!

so a grey horse with 1 copy of the gene will look the same as a horse with 2? and if it has one it CAN produce a foal without the grey gene?


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## Palindrome (20 June 2013)

horselessb said:



			Numpty question- whats a mutated version and a normal version?!

so a grey horse with 1 copy of the gene will look the same as a horse with 2? and if it has one it CAN produce a foal without the grey gene?
		
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Yes, chromosomes come in pair (it's the same for humans). The dam and sire each give one chromosome of their own pair to the offspring. It is random so there can be a lot of different combinations of chromosomes possible in each parent's gamete.
For example, the sexual chromosomes can be X and Y. A female is XX and a male XY. The dam can give either of her X chromosomes and the sire can either give X or Y, making the baby female or male.


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## cobalobM (20 June 2013)

Palindrome said:



			Yes, chromosomes come in pair (it's the same for humans). The dam and sire each give one chromosome of their own pair to the offspring. It is random so there can be a lot of different combinations of chromosomes possible in each parent's gamete.
For example, the sexual chromosomes can be X and Y. A female is XX and a male XY. The dam can give either of her X chromosomes and the sire can either give X or Y, making the baby female or male.
		
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ahhh its all coming back to me from biology lessons! so for a female- can X and X be different? or do they have to be the same?!  or is that completely wrong?! ahahhaha


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## cloppy (20 June 2013)

Dogrose, glad you said nearly always born a rich colour then greying out lol. Heres mine at a day old then 2yrs old last week.  Definately will grey out but think it will be a longish process.  You can just about see his silver tail in the picture.


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## Meowy Catkin (20 June 2013)

I spy a white marking on his off-hind! Could he have a Gulastra Plume (so sabino - hence the sock) and not Grey? He certainly doesn't seem to have any grey hairs on his head and that often greys out first.


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## cloppy (20 June 2013)

oo goodness never heard of Gulastra Plume before.  His mother was a grey connemara and his father a dark bay hanovarian.  He does have a few grey hairs scattered throughout his body, he also has the big white star that you can see on the first photo.  Funny you should say about the sabino as he does have an egg shell eye that is common in coloureds, does this mean anything?


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## Meowy Catkin (21 June 2013)

Gulastra Plume - basically it's one of the weird things that sabino can cause. Here's a couple of examples. Neither horse has the grey gene.













Note that both horses have jagged edges to their white markings, which indicates Sabino. It can also cause white flecks in the coat (in fact a maximum sabino has so many white hairs that the whole horse ends up being white - a true white, again different to grey).


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## Dogrose (21 June 2013)

cloppy said:



			Dogrose, glad you said nearly always born a rich colour then greying out lol. Heres mine at a day old then 2yrs old last week.  Definately will grey out but think it will be a longish process.  You can just about see his silver tail in the picture.














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There are always exceptions, but how do you know he will grey out? Is his dam tested homozygous? He doesn't look like he is grey but again, always exceptions 

ETA the lighter tail end does indicate grey.


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## Dry Rot (21 June 2013)

horselessb said:



			its very complicated!!  

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Correct!


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## cloppy (21 June 2013)

Thank you for the pics, I just assumed he would go grey as he is mottled between his back legs.  Heres a better pic of his tail.  The mare hasn't been tested.  Would be lovely if he stayed this colour.
Sorry OP for taking over your thread.  Hope we both learn something here.


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## Palindrome (21 June 2013)

horselessb said:



			ahhh its all coming back to me from biology lessons! so for a female- can X and X be different? or do they have to be the same?!  or is that completely wrong?! ahahhaha
		
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Yes, the female got one chromosome X from each of her parents and they can contain different versions (alleles) of the same genes. For each gene, you can see if she is heterozygous (different alleles) or homozygous (same alleles). The dominant gene will be the one expressed and will determine the phenotype (appearance). Some characters are the results of the combination of several genes so it can become more complicated.

For horse colours, there is a gene giving the base colour, black or chestnut, and then you have modifying genes than can alter the base colour:

- agouti is responsible for the body to go lighter (points, mane and tail stay dark). A black based horse with agouti is a bay, it does not really show up on a chestnut (although my chestnut mare gets darker legs in her Summer coat and I think she has agouti cause her dam was a bay),

- grey adds more and more white hairs to the coat as the horse ages

- cream makes the coat lighter, a black based horse with 1 cream gene is a smoky black, chestnut based with 1 cream is a palomino, black based with agouti (bay) and 1 cream is a buckskin. 2 cream genes makes the coat even lighter coloured: chesnut with 2 creams is a cremello ...

You also have champagne, dun, the pinto genes (tobiano, overo, sabino, splash...). Here are more detailed explanations on the different color genes: http://www.whitehorseproductions.com/equinecolor.html

An interesting factoid about horse colours is the case of the chesnut friesians. Black is dominant over chestnut so if a horse is heterozygous black (1 copy black and 1 copy chestnut), he'll be black. Genes are given randomly to the offsprings. If you breed 1 heterozygous black to 1 homozygous black, you will get 100% black horses with 25% being heterozygous black (so carrying 1 copy of the chestnut gene). If you breed 1 heterozygous black to another heterozygous black, you will have 25% chance of having a chestnut foal and 75% chance of black foal (in which 50% are heterozygous black). This means that in some very rare cases, chesnut friesian popped up here and there from black parents. I think they can be registered as pure breds but can't be bred from/to as the studbook doesn't want to keep the colour.
There is another interesting case with the sabino arabians.


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## Palindrome (21 June 2013)

cloppy said:



			Thank you for the pics, I just assumed he would go grey as he is mottled between his back legs.  Heres a better pic of his tail.  The mare hasn't been tested.  Would be lovely if he stayed this colour.
Sorry OP for taking over your thread.  Hope we both learn something here.
		
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Rabicano often accompanies sabino and is responsible for roaning on the flank and between back legs. Or do you mean mottled as with pink skin?


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## cobalobM (21 June 2013)

Palindrome said:



			Yes, the female got one chromosome X from each of her parents and they can contain different versions (alleles) of the same genes. For each gene, you can see if she is heterozygous (different alleles) or homozygous (same alleles). The dominant gene will be the one expressed and will determine the phenotype (appearance). Some characters are the results of the combination of several genes so it can become more complicated.

For horse colours, there is a gene giving the base colour, black or chestnut, and then you have modifying genes than can alter the base colour:

- agouti is responsible for the body to go lighter (points, mane and tail stay dark). A black based horse with agouti is a bay, it does not really show up on a chestnut (although my chestnut mare gets darker legs in her Summer coat and I think she has agouti cause her dam was a bay),

- grey adds more and more white hairs to the coat as the horse ages

- cream makes the coat lighter, a black based horse with 1 cream gene is a smoky black, chestnut based with 1 cream is a palomino, black based with agouti (bay) and 1 cream is a buckskin. 2 cream genes makes the coat even lighter coloured: chesnut with 2 creams is a cremello ...

You also have champagne, dun, the pinto genes (tobiano, overo, sabino, splash...). Here are more detailed explanations on the different color genes: http://www.whitehorseproductions.com/equinecolor.html

An interesting factoid about horse colours is the case of the chesnut friesians. Black is dominant over chestnut so if a horse is heterozygous black (1 copy black and 1 copy chestnut), he'll be black. Genes are given randomly to the offsprings. If you breed 1 heterozygous black to 1 homozygous black, you will get 100% black horses with 25% being heterozygous black (so carrying 1 copy of the chestnut gene). If you breed 1 heterozygous black to another heterozygous black, you will have 25% chance of having a chestnut foal and 75% chance of black foal (in which 50% are heterozygous black). This means that in some very rare cases, chesnut friesian popped up here and there from black parents. I think they can be registered as pure breds but can't be bred from/to as the studbook doesn't want to keep the colour.
There is another interesting case with the sabino arabians.
		
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Thankyou, thats really helpful, it says on that website that agouti only effects the black gene, so how is a chesnut effected by it?

and the cream gene doesn't effect black hairs unless its heterozygous? so a bay with 1 creme gene will be buckskin? as coat will lighten and black tail/mane will stay black?


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## cloppy (22 June 2013)

Here are some more  pics of him to explain the colouring.
His sock has the zig zag edges as you said







This is inbetween his back legs








and a close up of his belly


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## Meowy Catkin (22 June 2013)

It certainly looks like he has sabino. He could have grey as well, but I personally think that if his colour has been stable (ie he's not getting greyer) then he probably doesn't have grey.

If his dam has one copy of the grey gene, it would have been a 50/50 chance of her passing it on to him.


RE Agouti and chestnuts - the gene doesn't change their colour, but they can pass it on to their offspring. So if a chestnut (with one copy of agouti) has a foal with a homozygous black (two copies of black) then the foal will have a 50% chance of being black and 50% chance of being bay.


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## cloppy (22 June 2013)

Thank you, the dam has had other non grey foals, so only one copy of grey gene?


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## Meowy Catkin (22 June 2013)

Yes. One copy.


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## Palindrome (22 June 2013)

horselessb said:



			and the cream gene doesn't effect black hairs unless its heterozygous? so a bay with 1 creme gene will be buckskin? as coat will lighten and black tail/mane will stay black?
		
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 yes, smoky black is not much different than black but smoky cream (black with 2 cream genes) is much lighter.


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## Kacey88 (23 June 2013)

I have a question! I read that splash is an incomplete dominant gene. I think my mare has a minimal splash marking, so what does incomplete dominant mean? I know half her foals will get it (she's had a bay foal without it) so does it mean they can carry it, but not show it?


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## Meowy Catkin (23 June 2013)

A good example of an incomplete dominant is the cream gene. One copy has an effect on the coat colour (eg dilutes chestnut to palomino) but two copies are needed to show the full effect (eg dilute chestnut to creamello).

One copy of Splash white (SW1) will cause 'dipped in paint' leg and face markings with straight edges compared to horses with jagged edged sabino markings (although a horse can have both sabino and splash white).







If a horse has two copies of SW1, it will have far more white, including white on the body.







SW horses often have blue eyes, even if the white marking don't reach the eyes.

SW2 and SW3 are found in some Paint and Quarter horses, but from what I've read, they are lethal in their homozygous form.


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