Laipis P J, Van de Walle M J, Hauswirth W W
Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610.
Proc Natl Acad Sci U S A. 1988 Nov;85(21):8107-10. doi: 10.1073/pnas.85.21.8107.
Two polymorphic mitochondrial DNA genomes, differing by a single Hpa II restriction site, are present at significantly different levels in tissue of three sibling dairy cows. The relative ratio of the two heteroplasmic molecules varies 3-fold among these three animals and documents a rapid segregation of mitochondrial genotypes in mammals. DNA sequencing shows the difference is due to a single guanine at position 364 in bovine mitochondrial DNA. A model involving unequal partitioning of the two amplified mitochondrial DNA species during the early cell divisions of the embryo can explain the appearance of such variation in heteroplasmic sibling animals. The model provides a basis for understanding the rapid DNA sequence variation observed in vertebrate mitochondrial DNA despite its high copy number and strict maternal inheritance.
在三头同胞奶牛的组织中，存在两个多态性线粒体DNA基因组，它们仅相差一个Hpa II限制性酶切位点，且含量存在显著差异。这两种异质性分子的相对比例在这三头动物之间相差3倍，证明了哺乳动物中线粒体基因型的快速分离。DNA测序表明，差异是由于牛线粒体DNA中第364位的一个鸟嘌呤所致。一个涉及胚胎早期细胞分裂过程中两个扩增的线粒体DNA物种不均等分配的模型，可以解释异质性同胞动物中这种变异的出现。该模型为理解脊椎动物线粒体DNA中尽管拷贝数高且严格母系遗传但仍观察到的快速DNA序列变异提供了基础。
