Spastic Paresis

Does anyone know how Spastic pareseis works.  I assume it is a gentic disease but does it require both the sire and the dam to be carriers.  I beleive I have a calf that is developing this out of a sire that I would not exspect it from, though the dam would not surprise me.

there's a couple good threads on Spastic paresis (SP) on steerplanet (SP) tee hee.

recessive with incompletd penetrance, ie different severity, to meaning there may be more than one copy of the gene in a tandem repeat that may be the cause of the severity, or something else is going on.

list the pedigrees.  the other threads talk about a few pedigrees.

We had a lifeline steer with it and I have a friend who has a simmy steer with it now.  It is really sad to see them get progressively worst.  Ours didn't make it past 1000lbs before hitting the butcher shop.

I have seen a SP calf in it's extreme severity and it was a hideous sight. I believe it was sired by Dr. Who (which supposedly has two shots of Power Plant thru WMW and  Witch Doctor) and the dam had some Power Plant in her pedigree also. It was a total train wreak. 

We had a heifer with it out of Cherry Bomb. She was gorgeous as a calf till this developed. She didn't make it past 500 pounds before we sent her to the slaughter house.

We have a calf with it sired by Sunseeker and out of a Monsoon x Simm x Angus dam.