Will the Quantaray 49mm to 55mm step up ring work on a Sony a100 DSLR camera

If I'm reading this right, you had a Minolta dslr and had a 49mm lens on it and purchased a Sony dslr with a 55mm lens. You could use a step down adapter to put the 49mm filters on the 55mm lens but it would greatly reduce the picture quality. It would have an affect on the picture like closing one eye and look at your computer, then form an 'O' with your thumb and forefinger and put it up to your eye and look at your computer. That is the effect you would have with the smaller filter on the 55mm lens. I would suggest putting the 49mm lens from your Minolta on your Sony and just using your filters on that lens and purchasing a 55mm UV filter, or the set with UV, CPL (circular polarizing), and FD filter. These can be purchased on ebay fairly inexpensive. If your Minolta camera was digital and had auto focus and had a detachable lens it will fit on the Sony.
(press the button on the front of the camera where the red dot is on the side of the lens, and while you are holding the button down grasp the lens and turn it counterclockwise). Be extremely careful an not let any debris fall into the camera when the lens is off the camera! It is a good idea to tilt the camera slightly forward when the lens is off. Do not touch the mirror inside the camera when you have the lens off. You also have to be careful when changing lenses outside when it is windy. I hope this answers your question

The step-up ring will on any lens with a 49mm filter thread, regardless of the manufacturer. The easiest way to find out whether it works with any given lens is to see whether the ring fits onto the front of the lens (you could also read the filter size written on the lens itself).
If it doesn't fit, purchase the appropriate step-up ring. That will be much cheaper than buying a whole new set of filters.
If the new lens(es) have a 55mm filter thread then you don't need the step-up ring at all. The filters will mount directly onto the lens.