Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel.
Phys Life Rev. 2010 Sep;7(3):362-76. doi: 10.1016/j.plrev.2010.06.002. Epub 2010 Jun 4.
The genetic code maps the sixty-four nucleotide triplets (codons) to twenty amino-acids. While the biochemical details of this code were unraveled long ago, its origin is still obscure. We review information-theoretic approaches to the problem of the code's origin and discuss the results of a recent work that treats the code in terms of an evolving, error-prone information channel. Our model - which utilizes the rate-distortion theory of noisy communication channels - suggests that the genetic code originated as a result of the interplay of the three conflicting evolutionary forces: the needs for diverse amino-acids, for error-tolerance and for minimal cost of resources. The description of the code as an information channel allows us to mathematically identify the fitness of the code and locate its emergence at a second-order phase transition when the mapping of codons to amino-acids becomes nonrandom. The noise in the channel brings about an error-graph, in which edges connect codons that are likely to be confused. The emergence of the code is governed by the topology of the error-graph, which determines the lowest modes of the graph-Laplacian and is related to the map coloring problem.
遗传密码将 64 个核苷酸三联体（密码子）映射到 20 种氨基酸上。虽然很久以前就揭示了这个密码的生化细节，但它的起源仍然不清楚。我们回顾了信息论方法在密码起源问题上的应用，并讨论了最近一项工作的结果，该工作从进化、易错的信息通道的角度来处理密码。我们的模型——利用有噪通信通道的率失真理论——表明遗传密码起源于三种相互冲突的进化力量的相互作用：对不同氨基酸的需求、对容错性的需求以及对资源成本最小化的需求。将密码描述为信息通道，使我们能够从数学上识别密码的适应性，并在密码子到氨基酸的映射变得非随机时，在二阶相变处定位密码的出现。通道中的噪声产生了一个错误图，其中边连接可能混淆的密码子。代码的出现由错误图的拓扑结构决定，这决定了图拉普拉斯的最低模式，并与地图着色问题有关。
