Alexander Koch is an American actor best known for his starring role as James "Junior" Rennie — Big Jim's disturbed son who kidnaps Angie McAlister and keeps her hostage i his father's fallout shelter, in the science fiction television horror series Under the Dome, based on the novel by Stephen King.
Born and raised in Detroit, Koch was heavily involved in both local community and high school theatre productions. He attended the Theatre School at DePaul University and immersed himself in productions such as A Lie of the Mind, Hair, Intimate Apparel, Normal, Assassins and Reefer Madness: The Musical.
In 2012 he received his BFA in acting. Under the Dome marked his first series regular role on television and he made his film debut as Frank in Eddie O'Keefe's independent short film The Ghosts.
In his off time, Koch enjoys writing, music, playing the guitar and collecting vinyl records. He resides in Los Angeles.