(A) Cytoplasmic bridges form among oogonia in the germline cyst, leading to selective transfer of wild-type mitochondria (blue) to the primary oocyte, leaving mutant mitochondria (red) in nurse cells that then undergo apoptosis. (B) Cytoplasmic transfer which selectively pools of mtDNA from eight germline cyst cells into a single primary oocyte causes a large increase in the number of mitochondria (middle panel) and a large reduction in the mean (dotted line, bottom panel) and distribution of mutation load (yellow shaded area shows the 90% quantile, bottom panel), which persists during oocyte maturation. Pooling of mtDNA requires two fewer rounds of mtDNA replication to regenerate copy number in mature oocytes. Parameter values , . (C) Change in mutation load () across a single generation (median (red line) and distribution (box plot IQR with min/max whiskers and outliers)), for individuals with low (), medium (), and high () initial mutation loads, with variable strengths of selective transfer (). Parameter value , .