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Posted: Thu Apr 13, 2006 5:06 pm
by Ryan
Whereas I can understand the genetics of the short/non-short situation in Dexters, I haven't been able to find out much about the inheritance of coat colour (perhaps I've not been looking in the right places).
Can someone either please enlighten me, or point me in the right direction?
Any information can be pitched at a level as detailed/technical as you like.
Many thanks.
Posted: Thu Apr 13, 2006 6:42 pm
by Duncan MacIntyre
Black is dominant to Red. Black dexters may be carrying two black genes, but a minority will carry one black and one red. Red will show if the calf inherits a red gene from each parent.
BB x BB = 100% black
BB x BR = 100% black but 25% carry red
BR x BR = 25% black, 50% black carrying red, 25% red
BB x RR = 100% black carrying red
RR x RR = 100 red
Dun dexters are essentially black, but carry a gene which modifies the black. I think this is recessive so they need two dun genes to show the dun colour. at one time there was talk of all sorts of weird colours showing up if we mixed reds and dun but I don't know of any proven instances.
If you are working with blacks and duns, it will be quite straightforward that if
Dun x Black = 100% black
Dun x Black carrying dun = 50% dun, 50% dun carrying black
Dun x Dun = 100% Dun
Dun x red = Black
Hope I am not confusing everyone.
Duncan
Posted: Fri Apr 14, 2006 12:55 am
by Ryan
Great stuff. Thanks Duncan.
Posted: Fri Apr 14, 2006 7:06 pm
by Mark Bowles
Nice one Duncan, explained nice and simple even for the less genetic minded people.
Thanks
Mark
Posted: Sat Apr 15, 2006 9:41 pm
by Duncan MacIntyre
Thanks for comments, Mark, but I am not as helpful as it seems - I left out the issue of red carrying dun as I was in a bit of a hurry.
It seems that red can carry dun as well, but it will not show without the presence of black.
To show all the possiblilities I would need to extend my shorthand. There are a lot of possibilities.
Any one animal could be BB, BR, RR, BBD, BBDD, BRD, BRDD, RRD or RRDD.
BB looks black, carries neither red nor dun
BR looks black, carries red but not dun
RR looks red, carries neither black nor dun
BBD looks black but carries dun but not red
BBDD looks dun, carries black but not red
BRD looks black, carries and red and dun
BRDD looks black, carries red and dun
RRD looks red, carries dun but not black
RRDD looks red, carries dun but not black
This gives us quite a number of possibilities from all the differnent matings in terms of percentages of possibilities, but at the end of the day they will all be black, red or dun. As far as I understand things the red gene will not be affected by the presence of the dun gene, but both can be present in an animal as either single inheritance from one parent or double from both. If two reds are present the animal will be red regardless or presence of dun, if only one dun or one red is present the animal has to be black. I have just spent about half an hour looking at all the possibilities and have not yet worked out an easy way to post them all - not because it is complicated just that there are so many possible outcomes.I am actuallly beginning to feel a bit like the the dormouse in Alice in Wonderland who said that " I say what I mean is the same as I mean what I say" or words to that effect. I think what I have said is correct this time, and only a wee bit simplified the first post.
See Dex-Info.net for an article on the Dun gene.
Duncan
Posted: Sat Apr 15, 2006 10:39 pm
by Duncan MacIntyre
Sorry folks, I have just spotted a mistake in the master plan - BRDD will I think look Dun but carry black and red.
BRDD x RR would produce 50% red and 50% black
BRDD x RRD could I think produce red, black or dun
Please, someone tell me if I am talking nonsense. It all depends on whether or not it takes two blacks as well as two duns to make a dun.
Duncan
Posted: Sun Apr 16, 2006 12:36 pm
by Ryan
Duncan, going back to your original 13th April post, wouldn't the Dun x Black carrying Dun give 50% Dun and 50% Black carrying Dun (rather than Dun carrying Black)?
As far as the additional complicating issue of Red being able to carry Dun but only showing it in the presence of Black (15th April post), then I also think that BRDD will be Dun and carry both Black and Red, and that BRDD x RRD could give any of the three colours, but I'm still trying to get my head around the BRDD x RR giving 50% each of Red and Black...
..and my head is starting to hurt!
P.S. Just got to grips with it; not sure whether to post this now.
Posted: Sun Apr 16, 2006 3:37 pm
by Duncan MacIntyre
Of course you should have posted it, Ryan, that is why this is termed a "discussion board". I have a habit of rushing into print without proof reading what I have written, and it is so easy to see what you think you have said anyway. You are of course right about the Dun x Black carrying Dun, they would be 50% Dun and 50% Black carrying Dun. The reason the Black carrying red with two dun genes crossed with a RR (homozygous red, not carrying any black or dun genes) would be 50% red carrying dun and 50% black carrying dun is that half of them would inherit two red genes, one from each parent, and one dun: the other half would get one red and one black, hence be black, and carry one dun. None would be dun as one of the parents would not have any dun gene and two would be needed - each individual will only get one gene of each pair from each of the parents. I am presuming that the inheritance of the dun genes is completely independent of the inheritance of the red and black - the red and black occupy the same place so each will have two of either red or black so can be BB BR or RR. They can have dun or not, either singly as D or double DD, only DD will give a dun coloured animal and only if it carries black, as var as I know. It does worry me that I am setting myself up as a genetic expert which I am not - I am just trying to put what I understand of the subject into easy language. I hope anyone who thinks I may have got any of it wrong, or who spots the mistakes as you have done, will say so rather than lurking - nice to get lots of different contributors.
Duncan
Posted: Sun Apr 16, 2006 5:12 pm
by John C
Bimey !
The three I have are all black ,I'd like a red one to complete the set . As far as I know ,the ones that I have are black going back quite a way . I was intending to buy a red bull to give me a chance of a red calf but it looks as though I will be better off buying in a ready made one !
Posted: Mon Apr 17, 2006 9:23 pm
by Inger
Yes Duncan, the Dun is carried on a different allele, so its inheritance is a separate issue from the Black/Red, from what I understand from the articles I've read on the subject.
John C, you can certainly use a Red bull the first year, then all your calves will carry Red. In the next generation you can use another Red bull and have a 50% possibilty of a Red calf, or you could mate two of your calves (once grown) and you'll still have a 25% chance of a Red calf, but once again, another 50% of calves will carry Red. So its depends on how much patience you have. :laugh: