Polytene Chromosomes: It was discovered by Balbiani. They are found in permanent prophase stage. The size of the polytene chromosomes is $2000\mu m$. They were observed in the cell of salivary glands of Chironomus larva of Dipteran insect.

Special Characteristic: They become giant due to endomitosis or endoduplication. Large swellings are found on some places of each strand that are called puffs (Balbiani rings). In puffs, DNA is uncoiled for rapid transcription of RNA that undergoes translation to form proteins.