Jack and his Extra Y is a children's book for kids with 47, XYY. This book helps children and adolescents with XYY understand their condition. The story follows Jack, a young boy with XYY, through his busy day as he attends school, goes to golf practice and has a doctor's appointment. The story explores the genetics of XYY and addresses social, academic and medical aspects of this condition in an age-appropriate, fun way. Though Jack's condition presents him with many challenges throughout the story, he is able to work through each challenge in his own way. Boys with XYY will identify with and learn from Jack as they read this book.