These are generalizations, however, and the assumption of homoplasmy
can sometimes be false when a cell or individual possesses multiple mitochondrial genotypes giving rise to heteroplasmy.
The polyploid nature of the mitochondrial genome (up to several thousand copies per cell) gives rise to the important features of homoplasmy
, heteroplasmy [56-59], and clonal expansion of mtDNA, even in the same mitochondrion, with random mitochondrial segregations capable of occurring in mitochondria within the same cell [11,12].
The high mutation rate coupled with the polyploid nature of the mitochondrial genome gives rise to an important feature of mitochondrial genetics, namely homoplasmy
The consequence of these multiple ways of mixing and assorting mtDNA both within a single mitochondrion and the collected mitochondria of the cell as a whole leads to the concepts of homoplasmy
(where all mitochondrial genomes in a cell or organism are of the same sequence) and heteroplasmy (where two or even more mitochondrial genome types can be present simultaneously in an organism).
The elevated rate of nucleotide transition has been reported to show multiple vibrational events in specific nucleotide sites and increase the frequency of homoplasmy
(Meyer 1994; Simons et al.