The series of mitotic divisions which generate the nurse cell/oocyte clones that characterize insects with polytrophic meroistic ovaries (like Drosophila). In D. melanogaster two or three stem-line oogonia reside in each germarium (q.v.). Each stem cell (S) divides into two daughter cells. One behaves like its parent, and the other differentiates into a cystoblast (Cb). This cell, by a series of four mitoses (M1–M4), each followed by incomplete cytokinesis, produces a branching chain of 16 interconnected cells. In the diagram here, cystocytes (represented by open circles) belong to the first, second, third, or fourth generation. The area in each circle is proportional to the volume of the cell. The number of lines connecting any two cells shows the division at which the ring canal (q.v.) joining them was formed. Cells 14 and 24 enter the oocyte developmental pathway and form synaptonemal complexes (q.v.). These cells are therefore called pro- oocytes (q.v.). See insect ovary types, polyfusome, stem cell.
Subjects: Genetics and Genomics.