The process of oogenesis Development in the fly begins well before the moment of conception. Hundreds of genes participate in oogenesis, the building of the egg. The egg is a highly structured chamber. Its RNA, DNA and proteins do not roam freely, but rather are directed and controlled by the egg's dorsoventral polarity and anterior-posterior axis. Neither is the egg cell an independently created entity.
Follicle cells envelop the maturing, pre-fertilized egg.
Nurse cells provide nutrients the embryo will require, storing them in the yolk, as though filling pantry shelves in anticipation of future need. Budding from this terminal or polar region gives them their name. They are the germ line for the next generation, and also referred to as such. In effect, the ovary structure is built around these germ line stem cells. The separation of the pole cells from the rest of the developing embryo is one of the first events in morphogenesis.