Ishigami M, Nagano K
Orig Life. 1975 Oct;6(4):551-60. doi: 10.1007/BF00928903.
A new approach to the origin of the genetic code is proposed based on some regularities in the nucleotide distribution pattern of the code. The relative amounts of various amino acids in primitive proteins were possibly different from those in organisms living today. The primordial ratio was supposed to shift to the modern one guided by the action of primitive nucleotides. Each primitive tRNA had a discriminator site and, distinguished from it, an anticodon site. It also postulated that primordially each amino acid could correspond to a wide variety of codons. During the course of the evolutionary change, a selective mechanism worked among the protobionts so that less frequent nucleotides became associated with more abundant amino acids in the primordial conditions,thus finally leading to the present codon catalogue.
基于遗传密码子核苷酸分布模式中的一些规律，提出了一种关于遗传密码起源的新方法。原始蛋白质中各种氨基酸的相对含量可能与当今生物中的不同。原始比例被认为是在原始核苷酸的作用下转变为现代比例的。每个原始tRNA都有一个鉴别位点，与之不同的是，还有一个反密码子位点。该理论还假定，最初每个氨基酸可能对应多种密码子。在进化变化过程中，原生生物之间存在一种选择机制，使得在原始条件下，较少出现的核苷酸与更丰富的氨基酸相关联，最终导致了目前的密码子表。
