Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, UK.
Proc Biol Sci. 2012 May 7;279(1734):1777-83. doi: 10.1098/rspb.2011.2183. Epub 2011 Dec 7.
In evolution, the effects of a single deleterious mutation can sometimes be compensated for by a second mutation which recovers the original phenotype. Such epistatic interactions have implications for the structure of genome space--namely, that networks of genomes encoding the same phenotype may not be connected by single mutational moves. We use the folding of RNA sequences into secondary structures as a model genotype-phenotype map and explore the neutral spaces corresponding to networks of genotypes with the same phenotype. In most of these networks, we find that it is not possible to connect all genotypes to one another by single point mutations. Instead, a network for a phenotypic structure with n bonds typically fragments into at least 2(n) neutral components, often of similar size. While components of the same network generate the same phenotype, they show important variations in their properties, most strikingly in their evolvability and mutational robustness. This heterogeneity implies contingency in the evolutionary process.
在进化过程中，一个有害突变的影响有时可以被第二个突变所补偿，从而恢复原始表型。这种上位性相互作用对基因组空间的结构有影响，即编码相同表型的基因组网络可能不能通过单一的突变来连接。我们使用 RNA 序列折叠成二级结构作为模型基因型-表型图谱，并探索具有相同表型的基因型网络对应的中性空间。在这些网络中的大多数中，我们发现不可能通过单点突变将所有基因型相互连接。相反，具有 n 个键的表型结构的网络通常会分裂成至少 2(n)个中性组件，这些组件通常大小相似。虽然同一个网络的组件产生相同的表型，但它们在性质上表现出显著的差异，最显著的是在可进化性和突变鲁棒性方面。这种异质性意味着进化过程中的偶然性。
