Post by heathera on Mar 18, 2010 17:11:37 GMT -1
Starting this off and will add images and more explanation to it as brain, time and feedback allows.
Colour of your foal is determined by his/her parents and their ancestry. The easiest way to think about it is that you have lots of different layers, all of them are (sort of) independent of each other. What each layer shows is controlled by one gene donated by mum and one that is donated by dad. Each layer has two options.
One of the options is called dominant (it shows in the foal even if only one parent donates that option to the foal) and the other is recessive (it only shows if both mum and dad donate it)
Black or chestnut?
As an example the first layer to consider is whether your foal is going to be black or chestnut (if you think of chestnut as being 'no black hairs' it's a bit easier). A chestnut foal might be a bit of a shock in a purebred Dales as it's not a recognized colour
'Be black' (have black hairs) shown by the capital letter E is dominant to 'be chestnut' (have no black hairs) shown by the lower case e. Even if only one parent gives your foal the be black E option, the foal will be black. If your foal is black she will have been given a dominant black gene (E) from at least one of her parents.
She might have been given one from mum and one from dad making her EE.
She might also have a black option from mum (E) and chestnut as an option from dad (e)
A horse with one black gene (E) and one chestnut gene (e) would still look black as that black is dominant over chestnut.
A chestnut horse would have to be given one chestnut option from from mum (e) and one from dad (e) making her ee.
The interesting thing is that we can't say right now that chestnut does not exist in the Dales breed. We can say it's very unlikely but it may just be, like the foal syndrome, that the incidence of it is so low that we've never had two Ee Dales ponies mated so there's not been a chance for an ee foal to be born.
With me?
Bay or not bay?
The next layer we'll talk about is whether your horse is going to be bay or not. In order to be bay a horse must have an E option so there are some black hairs for the bay option to play around with, remember chestnut simply means 'my horse has no black hairs'. The bay option/gene makes the black hair appear in a certain pattern, usually in the mane and tail and from knee and hock down on the legs. The rest of the body is a brown colour. Bay is dominant to black so if even one parent gives the foal a bay (A) gene then the foal will be bay. So the two options for the letters here are A (bay) and a (not bay).
Let's take our black foal, she can be EE or Ee. If she is given a bay gene from mum (A) and a bay gene from dad (A) then she will be AA and will be bay herself. If the foal is given a bay gene from mum (A) and a not bay gene from dad (a) she will be Aa and still be bay as bay is dominant to not bay. You only need one copy of the 'be bay' gene for it to be shown. If mum gives her a not bay (a) and dad gives her a not bay (a) she will be aa and be black.
From this you can see we can't have a bay foal from black parents as neither mum nor dad will have a bay version of the gene to pass onto their foals, if they did it would show up and they would be bay themselves.
So far we've decided our black foal can be EE aa or Ee aa and our bay foal can be EE AA or EE Aa.
For interest chestnut horses can have bay foals. They are ee (no black from either parent) but they can 'carry' the 'be bay' gene. So a chestnut mare could be ee Aa. If they have a foal with a black stallion the foal could get the 'be black' gene from the stallion and the 'be bay' gene from the mare.
Going to turn grey or not going to turn grey?
Now let's look at grey. Grey is totally independent of all other colours we've talked about so far. All grey horses are born a base colour of either black or chestnut with the 'modifying' gene of bay either there or not. 'Be grey' (G) is dominant to 'don't be grey' (g) so only parent has to pass it on for the foal to 'be grey'. What 'be grey' does is cause the hair to turn white over a number of years. This means you cannot ever have a grey foal from two black or bay parents. It does work the other way around though in that you can have a black foal from two grey parents.
A grey horse is either GG (both parents had a grey version of the gene to pass to the foal) or Gg (one parent passed on the 'be grey' option, the other passed on the 'don't be grey' option). If two grey (Gg) horses have a foal they could both pass on the not grey (g) option and produce a gg (don't go grey) foal.
So, next time someone tells you your horse is grey and not black you can tell them that, actually, your horse is black, he's just greyed out
This brings me onto the vocabulary of homozygous (both gene options for a colour layer being the same e.g. EE or AA or GG) or heterozygous (the options being one of each e.g. Ee or Aa or Gg).
From what we've seen so far a horse that is homozygous for 'be grey' (GG) or 'be bay' (AA) will always produce grey or bay foals as they will always pass on a dominant version (G or A) of the option for that colour, turning that option 'on' as it were.
From what I have seen so far I don't think I've ever met a homozygous bay (AA) or grey (GG), all the Dales I've met that were either bay or grey have always had offspring that stayed dark and offspring that went grey. The only way to tell for sure is to do genetic testing. It's a 50:50 chance every time whether the parent passes on the grey (G) or the not grey (g), just because a grey mare has always produced grey foals you can't say she's always going to without the genetic test being done as she may just have always passed on the G option and not the g one.
Roan - the big debate.
Roan is, as you might guess, another layer in the pattern. It is also dominant, so two non-roan parents can't produce a roan foal.
It is totally separate from grey, the two options have nothing to do with each other apart from if a roan foal has a dominant 'be grey' gene (G) it will eventually turn grey all over.
What true roan does is make white hairs appear through the horses other body colour apart from on the head and legs.
If you aren't sure whether your young horse is greying out or simply a roan look at his/her parents first then look at his face.
Greying out horses tend to have white eye rings and faces and go grey from front to back. A true roan horse has a dark face and a greyish tinge to the rest of the body. Of the Dales genes the roan one is the most difficult to explain as it is now thought there may be different 'flavours' of the roan 'option'. There's a good explanation online. From what I can see I think the Dales only have one flavour of roan and that's true roan, the pattern described above.
There's a story going round that if you mate two heterozygous true roan horses (both are Rr) and they both pass on the 'be roan' (R) gene to make the foal homozygous (RR) then the foal will die in the uterus before s/he can be born. This has been proved by some research and disproved by other research but with the balance of thought at the moment being that it's a bit of an old wives tail as there is strong evidence now that homozygous stallions (RR) have been found in some breeds. New research is currently underway and we have DF members who are taking part in it with their roan ponies.
Colour of your foal is determined by his/her parents and their ancestry. The easiest way to think about it is that you have lots of different layers, all of them are (sort of) independent of each other. What each layer shows is controlled by one gene donated by mum and one that is donated by dad. Each layer has two options.
One of the options is called dominant (it shows in the foal even if only one parent donates that option to the foal) and the other is recessive (it only shows if both mum and dad donate it)
Black or chestnut?
As an example the first layer to consider is whether your foal is going to be black or chestnut (if you think of chestnut as being 'no black hairs' it's a bit easier). A chestnut foal might be a bit of a shock in a purebred Dales as it's not a recognized colour
'Be black' (have black hairs) shown by the capital letter E is dominant to 'be chestnut' (have no black hairs) shown by the lower case e. Even if only one parent gives your foal the be black E option, the foal will be black. If your foal is black she will have been given a dominant black gene (E) from at least one of her parents.
She might have been given one from mum and one from dad making her EE.
She might also have a black option from mum (E) and chestnut as an option from dad (e)
A horse with one black gene (E) and one chestnut gene (e) would still look black as that black is dominant over chestnut.
A chestnut horse would have to be given one chestnut option from from mum (e) and one from dad (e) making her ee.
The interesting thing is that we can't say right now that chestnut does not exist in the Dales breed. We can say it's very unlikely but it may just be, like the foal syndrome, that the incidence of it is so low that we've never had two Ee Dales ponies mated so there's not been a chance for an ee foal to be born.
With me?
Bay or not bay?
The next layer we'll talk about is whether your horse is going to be bay or not. In order to be bay a horse must have an E option so there are some black hairs for the bay option to play around with, remember chestnut simply means 'my horse has no black hairs'. The bay option/gene makes the black hair appear in a certain pattern, usually in the mane and tail and from knee and hock down on the legs. The rest of the body is a brown colour. Bay is dominant to black so if even one parent gives the foal a bay (A) gene then the foal will be bay. So the two options for the letters here are A (bay) and a (not bay).
Let's take our black foal, she can be EE or Ee. If she is given a bay gene from mum (A) and a bay gene from dad (A) then she will be AA and will be bay herself. If the foal is given a bay gene from mum (A) and a not bay gene from dad (a) she will be Aa and still be bay as bay is dominant to not bay. You only need one copy of the 'be bay' gene for it to be shown. If mum gives her a not bay (a) and dad gives her a not bay (a) she will be aa and be black.
From this you can see we can't have a bay foal from black parents as neither mum nor dad will have a bay version of the gene to pass onto their foals, if they did it would show up and they would be bay themselves.
So far we've decided our black foal can be EE aa or Ee aa and our bay foal can be EE AA or EE Aa.
For interest chestnut horses can have bay foals. They are ee (no black from either parent) but they can 'carry' the 'be bay' gene. So a chestnut mare could be ee Aa. If they have a foal with a black stallion the foal could get the 'be black' gene from the stallion and the 'be bay' gene from the mare.
Going to turn grey or not going to turn grey?
Now let's look at grey. Grey is totally independent of all other colours we've talked about so far. All grey horses are born a base colour of either black or chestnut with the 'modifying' gene of bay either there or not. 'Be grey' (G) is dominant to 'don't be grey' (g) so only parent has to pass it on for the foal to 'be grey'. What 'be grey' does is cause the hair to turn white over a number of years. This means you cannot ever have a grey foal from two black or bay parents. It does work the other way around though in that you can have a black foal from two grey parents.
A grey horse is either GG (both parents had a grey version of the gene to pass to the foal) or Gg (one parent passed on the 'be grey' option, the other passed on the 'don't be grey' option). If two grey (Gg) horses have a foal they could both pass on the not grey (g) option and produce a gg (don't go grey) foal.
So, next time someone tells you your horse is grey and not black you can tell them that, actually, your horse is black, he's just greyed out
This brings me onto the vocabulary of homozygous (both gene options for a colour layer being the same e.g. EE or AA or GG) or heterozygous (the options being one of each e.g. Ee or Aa or Gg).
From what we've seen so far a horse that is homozygous for 'be grey' (GG) or 'be bay' (AA) will always produce grey or bay foals as they will always pass on a dominant version (G or A) of the option for that colour, turning that option 'on' as it were.
From what I have seen so far I don't think I've ever met a homozygous bay (AA) or grey (GG), all the Dales I've met that were either bay or grey have always had offspring that stayed dark and offspring that went grey. The only way to tell for sure is to do genetic testing. It's a 50:50 chance every time whether the parent passes on the grey (G) or the not grey (g), just because a grey mare has always produced grey foals you can't say she's always going to without the genetic test being done as she may just have always passed on the G option and not the g one.
Roan - the big debate.
Roan is, as you might guess, another layer in the pattern. It is also dominant, so two non-roan parents can't produce a roan foal.
It is totally separate from grey, the two options have nothing to do with each other apart from if a roan foal has a dominant 'be grey' gene (G) it will eventually turn grey all over.
What true roan does is make white hairs appear through the horses other body colour apart from on the head and legs.
If you aren't sure whether your young horse is greying out or simply a roan look at his/her parents first then look at his face.
Greying out horses tend to have white eye rings and faces and go grey from front to back. A true roan horse has a dark face and a greyish tinge to the rest of the body. Of the Dales genes the roan one is the most difficult to explain as it is now thought there may be different 'flavours' of the roan 'option'. There's a good explanation online. From what I can see I think the Dales only have one flavour of roan and that's true roan, the pattern described above.
There's a story going round that if you mate two heterozygous true roan horses (both are Rr) and they both pass on the 'be roan' (R) gene to make the foal homozygous (RR) then the foal will die in the uterus before s/he can be born. This has been proved by some research and disproved by other research but with the balance of thought at the moment being that it's a bit of an old wives tail as there is strong evidence now that homozygous stallions (RR) have been found in some breeds. New research is currently underway and we have DF members who are taking part in it with their roan ponies.
That's brilliant Heather 
Ridgelane Duke 
Country Rose
