[Jacob-list] Horn Genetics

[sara young]

I am relatively new to all of this and bred my Jacobs for the first time last Fall to a four horned ram (I bought three pregnant ewes three years ago). Only one of my ewes is four horned, and her ewe twins both have SUED (minor) and poor, undeveloped horns (her first lamb had healthy eyes and horns). One of my ewes has no horns, and she had twin ewes also; one is four horned and the other is two, and the four horned ewe has blue eyes and striped horns. Her ewe from 2 years ago (who has two horns) also had twins - rams - and both were four horned. My last ewe had one of each, both two horned.
The random nature of genetics was so evident, and in spite of all of the studies I guess I still feel that it's not predictable...
And, I am keeping a variety of sheep to breed...based on fleece, disposition, coloring and horns.
(I found a home for my ewe and her twins with SUED where they will be pets and not bred).

Sara
  ----- Original Message ----- 
  From: Hobsickle at aol.com 
  To: snielsen at orednet.org ; jacob-list at jacobsheep.com 
  Sent: Sunday, July 17, 2005 7:10 AM
  Subject: Re: [Jacob-list] Horn Genetics


  In a message dated 7/16/05 11:23:02 P.M. Eastern Daylight Time, snielsen at orednet.org writes:
    A question for the Technician: is it that the gene for "4 horns" is
    dominant, or that the " polycerate gene" is dominant. I ask because,
    as we know, sometimes we get a sheep with more than 4 horns. And
    one wonders, what are the odds of a 6-horn condition, even if it
    were poorly expressed, passing on in a mating of 4-horn ram/6-horn ewe?

    Y'know, just to keep the answer from being too easy... ;-)

  Here's my opinion (and I'm sure some will disagree).  There is a single, dominant gene for abnormal cell migration/development in the embryo.  This ultimately (usually) results in multiple horns ("polycerate").  There is a real good chance that the number of horns in polycerates (2, 3, 4, 5, 6) is a result of either several different genes (loci), each exerting a mild influence -or- diet/environment -or- random chance -or- some combination of those factors.

  Anyone surprised at the "2" I put in the list of polycerate horn numbers?  While I'm not trying to say that all two-horns are polycerate, some must be!  If a polycerate animal can be three-horned (single horn on one side) why can't a "polycerate" animal have single horns on both sides?  


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