Rapid segregation of heteroplasmic bovine mitochondria

By following the transmission of a heteroplasmic mitochondrial DNA mutation through four generations of Holstein cows, we have documented that substantial shifts in the levels of heteroplasmy can occur between single mammalian generations, that neutral mitochondrial genotypes can segregate in different directions in offspring of the same female, and that a return to homoplasmy may occur in only two or three generations. This apparently rapid rate of mitochondrial DNA segregation in mammals contrasts to the much slower rates observed previously in insects and suggest fundamental differences between taxa regarding the mechanisms of mitochondrial gene transmission.