Polytene Chromosomes

Polytene chromosomes are a type of chromosome found within a special type of cell, usually in the salivary gland, Malpighian tubules, and midgut of insects. Polytene chromosomes consist of multiple copies of the same chromosome which have been "fused" together and extended, creating a visible chromosome with a banding pattern. Polytene chromosomes are important to the study of genetics because their visible banding pattern allows geneticists to identify, analyze, and compare the structure of chromosomes from different species. Polytene chromosomes can also be used to analyze the effects of radiation, chemicals, or mutations on a chromosome's structure. Moreover, polytene chromosomes can provide insight into the evolutionary relationships among different species.