homozygous dun or red??

[rhonda]

I am puzzled by something--- when I see an ad listing a red homozygous dun or a homozygous for red and dun how does that work?? When I had Paint horses--a horse that was homozygous for spots could only throw spotted foals--- how does a red be homozygous for dun or dun be homozygous for red without being that color?? And does it mean if that animal is homozygous for a certain color it will only produce that color??

[wdd]

Oh Gene don't be boring . Just think of all the differrent shades and variety you get with red. With black you only get black. Even Brenn likes to throw a little red every so often.

If you breed two reds you will only get red even if they carry dun. As Gene said the red overrides the dun. So genetically a Dexter can be homozygous red and dun at the same time but will only display the red coloration. If you bred that animal to a black that carried dun or a dun then you could get a dun animal or a black (unless they also carried red then you could still end up with red). Check out the genetic informaion tab on the ADCA website and pick Basic Concepts of Dexter Color Genetics it is explained there.

[Clive]

Red is the only colour that breeds true 100% of the time. Cross a red with a red, and you get red. Tell me if I'm wrong, but that's what everyone tells me and it has worked so far on my farm (but I've only used one bull).

He's a "very red" bull, not tested but he throws a lot of reds and looks very red. I also have a loads of black cows that will throw almost nothing but red calves when put to this bull. There are about 6 or 7 cows involved, each has had 4 or 5 calves each, and only 1 black calf in the whole lot. Must be just a run because even if the bull is 100% true-red, 25% of the calves should be black!

My next bull that I have kept because he is relatively small and very beefy, is by this red bull, out of a dun cow, but he is black. Presumably he will throw reds and blacks, and maybe duns if put to a dun? I'm glad there's only three colours

[rhonda]

But--if they are homozygous can they only throw the color they are homozygous for?? Can a bull be red but be homozygous for dun and only have dun calves?? Or does homozygous not work that way in cattle?? I thought based on Paint or Appaloosa horses if they are homozygous they will only throw color so if a bull is homozygous for dun it could only throw dun regardless of the cow color?? If you only wanted dun cattle would a homozygous for dun bull give you only dun calves???

[kansasdexters]

Hi Rhonda,

A cow or bull that is homozygous red and homozygous dun (remember that the dun gene occurs on a different chromosome than red or black); can produce red calves (when bred to another red); and can also produce dun calves (when bred to a dun).

A dun animal is genetically black. It always has at least one black gene (E^D/E+, E^D/e, or E^D/E^D) and it is also homozygous for dun (b/b).

Because there must be a gene for black (E^D) present, in order for homozygous dun (b/b) to be expressed as dun -- you don't see dun expressed when an animal is homozygous for red (e/e or E+/e or E+/E+) and homozygous for dun (b/b). Being homozygous for red means that both genes on the chromosome are red (no black gene), so only the red is expressed.

Hope this helps.

Patti