遗传密码子的通用性与特殊性

遗传密码子的通用性与特殊性是生物多样性的重要分子基础。本文就目前研究较多的热点密码子在线粒体和原生动物纤毛虫中的特殊性进行总结，并对其形成理论机制进行探讨，阐明变异密码子在线粒体中是通用密码子在漫长进化过程中的遗物，但在纤毛虫中则并非单一地由某个时间或从某个种类开始，而是独立多次地在各物种内分别产生。

The Universality and Particularity of Genetic Codes

The universality and particularity of genetic codes are important molecular basis of biological diversity. Code usage variation has been studied in the mitochondria and some species of ciliates, which have some non canonical genetic codes. These new data with those previously reported implicate that in the mitochondria, code usage variation is the relic of endless evolution of universal codes. In ciliates, it demonstrates that (i) utilization of UAA and UAG codes occurs to different extents among, but also within, the different classes of ciliates and (ii) the resulting phylogenetic pattern of deviations from the universal code cannot be accounted for by a scenario involving a single transition to the unusual code. Thus, contrary to expectations, deviations from the universal genetic code have arisen independently several times within the phylum.