The Variation Within

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Science  17 Nov 2006:
Vol. 314, Issue 5802, pp. 1050
DOI: 10.1126/science.314.5802.1050a

Uniparental (usually maternal) inheritance of a single type of mitochondrial genome, referred to as homoplasmy, has long been assumed to be the main mitochondrial state in eukaryotes. However, rare examples of multiple mitochondrial types within an individual, a state known as heteroplasmy, have been identified in animals, fungi, and plants.

Previous greenhouse studies indicated that heteroplasmy can occur in the bladder campion plant (Silene vulgaris), but Welch et al. show that it can be found at frequencies of up to 26% within a natural population. Furthermore, mothers that were heteroplasmic were shown to pass it on to their offspring, and the pattern of inheritance suggested that heteroplasmy was genome-wide (in the mitochondria) and not locus-specific. Although these findings may be taken as consistent with biparental inheritance, the fact that high levels of cytoplasmic male sterility, caused by cytonuclear interactions, are known to occur in S. vulgaris suggests that heteroplasmy may be selected for within female individuals in some populations. — LMZ

Genetics 174, 829 (2006).

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