There are certain interesting structures associated with the bands in the giant chromosomes called chromosome puffs or Balbiani rings. The swelling is bands at certain stages are given the name chromosome puffs. It is quite possible that these puffs are associated with the metabolic activities and represent areas of active RNA synthesis. According to Beerman and Bahr (1954), the coils in the puff region open out to form many loops. The larger chromosome puffs are called Balbiani rings and they show a high DNA and mRNA content.