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Re: [RC] Black Stallion Imax - heidiIn a message dated 1/19/2004 11:39:19 AM Central Standard Time, bgloverhrsewmn@xxxxxxxxxxx writes: I was all bothered, because a non-pregnant grey mare, laid down and had a black foal in one second. "Grey, black. hmmm. What are the genetics of that. Nobody even knew she was pregnant, and there had to be another black stallion around to sire that foal, and nobody mentioned that either. Why didn't they use chestnut?" I have an arab that is registered black and does not have a black in his pedigree at all.....He is 16 going on 17 so he will not change colors now I would think...mb The genetics of a grey mare having a black foal could be GgEEAa or GgEeAa or GgEEaa or GgEeaa. Or even no big E's if the sire contributed one. In order to be black, the foal must be ggEEaa or ggEeaa. So the mare had to be heterozygous for the greying gene (G) in order to transmit a small g to the foal, and had to have at least one recessive agouti gene (small a) to pass on as well. Greys can have a base coat color that is either black (big E) or red (two small e's), and the mare could have been either one--if she had a big E she could have passed it on--if she didn't, the foal could have gotten it from the sire. To convert that to "plain English"--a horse either has black pigment or he doesn't. Black pigment is dominant and is big E. A horse with no big E has two recessive genes (ee) and is red-based. The grey gene acts on either base color--it is dominant. So no matter if the horse has black pigment or not, if it has a big G, it will turn grey. So bays, chestnuts, and blacks are all recessive for grey, or gg. But a grey parent can be heterozygous and have a small g hiding in there to pass on, hence having non-grey foals. The agouti gene acts to segregate black pigment to the points. It can only act if there is black pigment present, so chestnuts are not affected by the agouti gene (A). It is dominant, so if even one copy is present in a black-pigmented horse, that horse will be bay. So in order to be black, the horse must have two recessive copies of the gene (aa). So to recap, as long as the mare had one copy of the small g and one copy of the small a, it is entirely possible for her to have a black foal. Hope that was somewhat clearer than mud, anyway... Heidi =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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