(I) Beginning in 1979, neuropsychologist Nancy Wexler and her colleagues travelled to a small village in Venezuela where the inhabitants exhibited a startlingly high rate of neurodegeneration. (U) Her team spent several years collecting tissue samples from large families there. (Ill) Fourteen years later, in 1993, her research team identified the single gene that causes Huntington's disease, an incurable degenerative disorder that affects muscle coordination and cognitive function. (IV) This breakthrough discovery was one of the first successful attempts to identify a gene associated with a disease. (V) The collection of samples was rather difficult.