Polytene Chromosomes

Polytene chromosomes from salivary glands of Drosophila virilis larvae

 Polytene chromosomes are produced by DNA replication without cell division, resulting in many chromatids lined up side by side. Polytene chromosomes occur in a variety of organisms, but are particularly well known from the salivary glands of Drosophila larvae.

Polytene chromosomes can be very large, and when stained these chromosomes and the banded patterns of staining can be seen clearly with an ordinary light microscope. The chromosomes shown here were prepared from the salivary glands of a Drosophila virilis larva by a student in Augsburg’s genetics class.