Polytene Chromosomes in Salivary Glands

Polytene chromosomes are giant interphase chromosomes made of many DNA strands aligned side by side. They were first described by Balbiani in 1881. They are often called salivary gland chromosomes because they are regularly seen in salivary gland cells, especially in Drosophila.

These chromosomes...

Typically, when a diploid cell divides, it first duplicates each of its chromosomes. Then, the cell distributes a copy of each chromosome between the two daughter cells so that each daughter cell receives a complete set of chromosomes.

Certain cells undergo multiple cycles of chromosome duplication without undergoing any cell division. Su...