Two ways to make an mtDNA bottleneck

Abstract

Rapid changes in mitochondrial DNA allele frequency between generations have been explained by an ‘mtDNA bottleneck’ in the germ line, and mtDNA aggregates, or nucleoids have been recently proposed to drive such a bottleneck. Now, a new study finds a sharp reduction in mtDNA content in the germ line and suggests that such reduction alone may account for the bottleneck effect.

Figure 1

(a) The problem: A simple model of the mitochondrial bottleneck contains too many mtDNA molecules and creates less estimated genetic drift (solid line) than experimentally observed genetic drift (dotted line). (b) Assuming aggregation of mtDNA molecules into nucleoids results in a much tighter effective bottleneck and thus accelerates the estimated drift to fit observations (4). (c) Alternatively, observed drift can be accounted for by a variable bottleneck with temporal reduction of copy number as described in this issue 3.