red roan with black points - what's the genetics?

[Susara]

A woman I know has a strawberry roan with black tail, lower legs and mane, and I was wondering what the genetic make-up for that would be. His head is solid chestnut, not black. The black on his legs go exactly where the solid colour of a typical roan would have; up the lower legs to the 'knees', ending in a point.

Unfortunately I don't have a picture, but it's a very pretty combination, especially since his chestnut is quite red so you get a beautiful red roan body set off against the pitch black points.

[chev]

He's a bay roan - that's a bay base with the roan gene. Also known as red roan. The roan gene mixes white hair in with the bay body colour, but leaves the mane, tail, legs and head unaffected, so the head stays bay and the points stay black, just as they would be on a bay pony.

A strawberry roan (or chestnut roan) is chestnut with the roan gene, which gives a body that's mixed white and chestnut hair and chestnut mane, tail and legs.

Black (or blue) roan is black with roan; on these horses, the white on the body gives them a blue-grey apperance, while the head, legs, mane and tail stay black.

[Susara]

Ok thanks, didn't realise that the bay is really 'one' genetic pattern, I thought the black mane and tail of a bay was a pattern 'on top of' a chestnut. But my knowledge of genetics is pretty limited and I'm only starting to figure out the basics.

Interesting that you say bay roan = red roan, I though chestnut roan = strawberry roan = red roan.

But then the terminology does get very confused.

[chev]

If you go into the genetics and colouring forum and set it to show posts from the beginning, you'll find several threads explaining how the coat colours work. :)

The base colour of a horse is dictated by one colour gene; that's called the Extension gene. Every horse has two copies of the Extension gene; one it inherits from mum, and one from dad.

If the Extension gene is 'enabled' to show black pigment, it's noted as 'E' and the horse is black. A horse only needs one enabled E gene to be black.

If the gene is not enabled to show black, it's noted as 'e'. If a horse has two 'e' copies, it'll be chestnut.

These two colours, black and red (or chestnut) are the two base colours. Every other colour, shade and pattern is caused by what's called 'modifiers' - that's alleles or genes that change the appearance of the coat colour.

Bay is one such modifier. On black horses, it works by restricting the black pigment to the points; hence the black legs, mane and tail of the bay horse. On chestnut horses, the effects can't be seen, since chestnut horses can't carry black pigment anyway.

Roan is another modifier. It causes white hair to be mixed in with the base colour on the body, but not on the points or on the head.

Terminology does vary slightly, but the terms I used are those most widely recognised.

So; if the horse has black points, we know that he has a base coat that's black; he has a bay modifier to restrict the black to the points, making his colour bay; and he carries roan, making him a bay (or red) roan.

You might find these threads useful to explain it in more detail.... :)

Roan thread (http://www.newrider.com/forum/showthread.php?t=47385)

Black, bay and chestnut thread (http://www.newrider.com/forum/showthread.php?t=47380)