SREL Reprint #2324

Heteroplasmy and organelle gene dynamics

Ronald K. Chesser

Department of Genetics, University of Georgia, Athens, Georgia 30602
Savannah River Ecology Laboratory, Aiken, South Carolina 29802

Abstract: This study assesses factors that influence the rates of change of organelle gene diversity and the maintenance of heteroplasmy. Losses of organelle gene diversity within individuals via vegetative segregation during ontogeny are paramount to resultant spatial and temporal patterns. Steady-state losses of organelle variation from the zygote to the gametes are determined by the effective number of' organelles, which will be approximately equal to the number of intracellular organelles if random segregation prevails. Both rapid increases in organelle number after zygote formation and reductions at germ lines will reduce variation within individuals. Terminal reductions in organelles must be to very low copy numbers (<5) for substantial losses in variation to occur rapidly. Nonrandom clonal expansion and vegetative segregation during gametogenesis may be effective in reducing genetic variation in gametes. If organelles are uniparentally inherited, the asymptotic expectations for effective numbers of gametes and spatial differentiation will be identical for homoplasmic and heteroplasmic conditions. The rate of attainment of asymptote for heteroplasinic organelles, however, is governed by the rate of loss of variation during ontogeny. With sexbiased dispersal, the effective number of gametes is maximized when the proportional contributions of the sex having the higher dispersal rate are low.

SREL Reprint #2324

Chesser, R.K. 1998. Heteroplasmy and organelle gene dynamics. Genetics 150:1309-1327.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).