Mitochondria and germ-cell death

In birds and mammals, most of the female germ cells are destroyed before fertilization in a process known as atresia, reducing the population of cells to a small fraction of that present in early fetal life. We suggest that this death of germ cells can be interpreted as a developmental solution to the accumulation of mutations (Müller's ratchet) in mitochondria, an idea that is supported by comparative analysis. Atresia in effect therefore removes oocytes carrying mutant mitochondria1.