Monkey Mouth

I am wondering if there is any updated research on monkey mouth.  I pulled DL's quote from an old post:

Monkey mouth is believed to be a recessive trait with variable penetrance - meaning that you can see widely varied phenotypes - from the calf that looks like a French bulldog without incisors to the calf whose botton jaw is an inch or more longer that the top making it hard for him to eat.

We have a cow that has thrown her second monkey mouth calf (this is her second calf).  She does go back to JDS Stout, who goes back to Power Plant, so I figure she is a big part of the problem.  My question is whether there is any information showing that the dam can be the only carrier for it to be expressed in the calf or is it truly a recessive trait requiring both dam and sire to be carriers?

What were the sires of both calves? Yes, Power Plant throws monkey mouth but the calves I've seen, seem to always have Maine (or some Cunia) on both sides of the pedigree. I do not believe I remember seeing monkey mouth in the F1 Maine's of the 70's and 80's.

I don't think they like to talk about genetic defects on this board. If you can keep the newbies in the dark it is usually better.

The calf last year was by DCC Faultless, which has Power Plant 2 generations back.  The cow herself has JDS Stout 3 generations back.  The cow is half MA and half Simmie. 

As for this year's calf, I have been in contact with the bull owner and will leave it at that.  The reason that I am being careful here is that unlike DCC Faultless, the unnamed bull's pedigree does not indicate any known monkey mouth carriers, which is why we used this bull on this cow.  I think we will breed the cow to Fat Butt or something with no Maine the next time around.