A lampbrush phase in oocytes of Drosophila and its bearing upon mutagen sensitivity data

Abstract

An autoradiographic study of RNA synthesis on S, oocyte chromosomes of D. melanogasler was performed together with a renewed light microscopic investigation of this stage. Corresponding oocyte stages inD. hydei and D.funebris were also studied. It is evident that the meiotic chromosomes of these species pass through a lampbrush phase at the end of pachytene. Transcriptions on both hetero‐ and euchromatin in the genome were confirmed during the lampbrush phase in D. melanogasler. The lampbrush phase seems to parallel a decreased mutation sensitivity known to occur during this stage of oocyte development. Oocytes of the more mutation sensitive D. melanogasler mutant c(3)G also pass through a lampbrush phase.