[Jacob-list] Horn Genetics

[Hobsickle at aol.com]

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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