Transcription of Polytene Chromosomes and of the Mitochondrial Genome in Drosophila melanogaster
This extract was created in the absence of an abstract.
Excerpt
TRANSCRIPTION IN SALIVARY GLAND NUCLEI
Polytene chromosomes, such as the ones found in Drosophila salivary glands, are particularly suited for cytological studies on RNA and DNA synthesis. During polytenization, DNA strands do not separate following replication; the resulting giant chromosomes provide a level of cytological resolution that can be obtained in few systems. It is possible to identify specific genetic regions throughout the cell cycle because the chromosomal structure remains intact during and between periods of DNA replication. However, the local chromosomal structure may change during periods of RNA synthesis. Many chromosomal regions actively engaged in RNA transcription undergo a phenomenon known as puffing, in which the banding structure becomes diffuse and the chromosomal diameter increases.
Changes in puffing pattern occur in response to various stimuli, including nutritional (Beermann 1973), developmental (Beermann 1952; Becker 1962; Berendes 1965, 1966; Ashburner 1967), metabolic (Ritossa 1962; Berendes et al. 1965; Ashburner 1970), and...
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↵* Present address: Department of Biochemistry and Biophysics, University of California Medical School, San Francisco, California 94143.
