Cedergren R J
Can J Biochem. 1982 Apr;60(4):475-9. doi: 10.1139/o82-056.
Extensive sequence data on mitochondrial (mt) tRNAs give for the first time an opportunity to evaluate tRNA gene evolution in this organelle. Deductions from these gene structures relate to the evolution of tRNA genes in other cellular systems and to the origin of the genetic code. Mt tRNAs, in contrast to the prokaryotic nature of chloroplastic tRNA structure, can not at the present time be definitely related to either prokaryotic or eukaryotic tRNAs, probably because of a higher mutation rate in mitochondria. Fungal mt tRNAs having the same anticodon and function are generally similar enough to be considered homologous. Comparisons af all mt tRNA sequences contained in the same mitochondrion indicate that some tRNAs originated by duplication of a prototypic gene which, after divergence, led to tRNAs having different amino acid specificities. The deviant mt genetic code, although admittedly permitting a simpler decoding mechanism, is not useful in determining whether the origin of mitochondria had preceded or was derived from prokaryotes or eukaryotes, since the genetic code is variable even among mitochondria. Variants of the mt genetic code lead to speculation on the nature of the primordial code and its relation to the present "universal" code.
线粒体（mt）tRNA的大量序列数据首次为评估该细胞器中tRNA基因的进化提供了机会。从这些基因结构得出的推论与其他细胞系统中tRNA基因的进化以及遗传密码的起源有关。与叶绿体tRNA结构的原核性质不同，目前mt tRNA无法明确地与原核或真核tRNA相关联，这可能是因为线粒体中的突变率较高。具有相同反密码子和功能的真菌mt tRNA通常相似到足以被认为是同源的。对同一线粒体中包含的所有mt tRNA序列进行比较表明，一些tRNA起源于原型基因的复制，该原型基因在分化后产生了具有不同氨基酸特异性的tRNA。尽管公认异常的mt遗传密码允许一种更简单的解码机制，但它对于确定线粒体的起源是先于原核生物还是真核生物，或者是从原核生物或真核生物衍生而来并无帮助，因为即使在线粒体之间遗传密码也是可变的。mt遗传密码的变体引发了对原始密码的性质及其与当前“通用”密码关系的推测。
