The effects of different levels of genetic exchange on organelle evolution.

Each mitochondrion and chloroplast organelle has tens to hundreds of genomes, and there are tens to hundreds of such organelles within each cell. This results in a genetic organization generating a population structure akin to a geographically structured population. Since genomes and organelles replicate and gene conversion can occur between copies, this offers the possibility for directional evolutionary forces acting within the cell. The consequences of genetic exchange within the cell (between genomes within an organelle and between individual organelles) and between individuals (biparental inheritance) when within-cell directional forces are present is examined. The net effect of genetic exchange is to increase the importance of any directional forces present within the cell. The consequences of within-cell forces when the variants they act on also have fitness consequences for individuals are also examined.