Casane D, Dennebouy N, de Rochambeau H, Mounolou J C, Monnerot M
Centre de Génétique Moléculaire CNRS, 91198 Gif-sur-Yvette Cédex, France.
Genetics. 1994 Oct;138(2):471-80. doi: 10.1093/genetics/138.2.471.
One unusual property of rabbit mitochondrial DNA (mtDNA) is the existence of repeated 153-bp motifs in the vicinity of the replication origin of its H strand. Furthermore, every individual is heteroplasmic: it carries mtDNA molecules with a variable number of repeats. A systematic study of 8 females and their progeny has been devised to analyze mtDNA transmission through generations. The results suggest that three mechanisms are acting simultaneously. (1) Genetic drift in the germ line is revealed by the evolution of heteroplasmy when two major molecular forms are present in a female. (2) A high mutation rate (around 10(-2) per animal generation) generating molecular diversity, by deletion and addition of repeated units, is required to explain the observation of heteroplasmy in every individual. Moreover, the rates of mutation from the most frequent type to the other types are unequal. The deletion of one unit is more frequent than a deletion of two units, which is in turn more frequent than a deletion of three. (3) Selection for shorter molecules in somatic cells is probable. The frequency distribution of mtDNA types depends on the organ analyzed (kidney-spleen and liver vs. gonads).
兔子线粒体DNA（mtDNA）的一个不同寻常的特性是，在其H链复制起点附近存在重复的153碱基对基序。此外，每一个体都是异质性的：它携带的mtDNA分子具有可变数量的重复序列。已设计了一项对8只雌性兔子及其后代的系统性研究，以分析mtDNA的世代传递情况。结果表明，三种机制同时起作用。（1）当雌性兔子中存在两种主要分子形式时，异质性的演变揭示了生殖系中的遗传漂变。（2）为了解释在每一个体中观察到的异质性，需要一个高突变率（每动物世代约10^(-2)），通过重复单元的缺失和添加来产生分子多样性。此外，从最常见类型到其他类型的突变率是不相等的。缺失一个单元比缺失两个单元更常见，而缺失两个单元又比缺失三个单元更常见。（3）体细胞中可能存在对较短分子的选择。mtDNA类型的频率分布取决于所分析的器官（肾脾和肝脏与性腺）。
