DNA Amplification in DNA Puff II/9A of Sciara coprophila

Abstract

Initiation of DNA replication is the most important control point in the cell cycle. Once a cell crosses the G1 to S boundary, it is committed to traverse the whole cell cycle until it comes back to G1, where it can remain indefinitely or continue to recycle. The mechanism of regulation of initiation of DNA replication is not yet understood in eukaryotes. In fact, there is such a paucity of information that even the sequences which are recognized as origins of replication are not yet defined in metazoa. As a model system to study these questions, we have used DNA puff amplification in the giant salivary gland chromosomes of the fungus fly, Sciara coprophila.