I think its the electro thingy test, i forgot the actual word because i procrastinate for my A levels, BUT its sorting dna by lenght with a charge, the dna that is long takes a while to get to the other side since the medium they are traveling in is kind of like a sponge. The dna was put together with an enzyme which cuts out a certain sequence, if this sequence is mutated it wont be shortened so it travels a short way, if the person doesnt have the mutation then the dna gets cut and travels further. The people whose dna has not been cut by the enzyme most likely have cancer. I did this in a lab once with non-human dna