 The disease allele usually contains 34-52 CAG repeats, but can contain as few as 32 or more than 100, and can expand in size when transmitted to successive generations.How the polyglutamine expansion in ataxin-2 leads to these symptoms is unknown.In 2010, work from Aaron Gitler and Nancy Bonini at the University of Pennsylvania discovered that intermediate-size CAG repeat expansions are significantly associated with risk for developing amyotrophic lateral sclerosis (Lou Gehrig's disease).