"You'll recall the great discoveries, for example in Cystic Fibrosis and [Muscular] Dystrophy; they all used these kinds of techniques. The technique is basically very simple. What it involves is looking at normally occurring variants in DNA that are spaced all along the 3 billion base pairs of DNA that make up our genome, and asking a simple question: If we have a large family in which some people have the disease and some don't, can we find DNA variants that are only seen when the disease is present? And if you find that kind of correlation, you will know that that DNA variant resides in a neighborhood in a genome that has to be near the disease-causing gene. So if you find a variant and if you find a correlation, then you can hone in and figure out what the gene is. It's a little bit, for example, like trying to find essentially a burning house by looking first from a satellite. Where with a Google image, you might see a little tiny plume of smoke but if you then fly over with an airplane you can figure out is it in the Northeast? What state is it in? What town is it in? Then you can track down the street and ultimately the burning house. That's a little bit what gene-linkage is like. "