POLYTENE CHROMOSOMES & CHROMOSOME To stain and identify the
polytene chromosomes of the salivary glands of Drosophila
melanogaster. To induce puffing, which is a visual indicator of
RNA transcription. Many larval and some adult tissues of insects
in the family Diptera are characterized by nuclei with giant
chromosomes. These chromosomes develop by multiple replications
of the chromosomes within each cell during development. Each
nucleus will contain hundreds of copies of each chromosome.
Cells are considered polyploid if they have more than two copies
of each chromosome. If the chromosomes align perfectly forming
large cables of chromosomes they In Drosophila melanogaster,
chromosomes of the larval salivary gland contain about 1024
copies of the DNA, or ten doublings from the normal 2n
condition, of each of the three chromosomes. Each gene is
exactly aligned with its homologs on the other 1023 copies. The
pattern of condensed regions (heterochromatin), and transcribed
regions (euchromatin) gives a series of a