The dappled gene is hidden and needs two recessive copies to be 'present' on the horse.  So a horse with no dapples is something like DaDa (Da/Dap being what most people just assume would be the name of the gene), a carrier would be Dada, and a horse showing would be dada.  You can figure out if your horse is a carrier when they throw a dappled foal.  If a non-dappled horse has a dappled foal (with the other parent being dappled or a carrier) then it can be assumed that the horse is a carrier for dapples.

For example - this wild Clydesdale is a chestnut, but her first foal and a few others since have shown dapples.  It means she's a carrier, so I put it in her name. If a dappled horse has a foal, it can assumed to be a carrier. As for reverse dapples, I'm not entirely sure what that is. If you're talking about 'silver dapple' than I think it's just considered a color, and not a visual image on the horse (at least at the moment). This paint foal is a "silver dapple" but it's not actually considered a horse with the dada gene.

reverse dapple is just a rare variation of dapple like skewed duns and roans. though i can't remember if it works like every other pattern variation (as in the specific variant has a chance of being passed down to foals).

@forgottenland - thank you!  I haven't seen a reverse dapple yet, lol.