Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
Crit Rev Biochem Mol Biol. 2010 Aug;45(4):257-65. doi: 10.3109/10409231003786094.
The discovery of the genetic code provided one of the basic foundations of modern molecular biology. Most organisms use the same genetic language, but there are also well-documented variations representing codon reassignments within specific groups of organisms (such as ciliates and yeast) or organelles (such as plastids and mitochondria). In addition, duality in codon function is known in the use of AUG in translation initiation and methionine insertion into internal protein positions as well as in the case of selenocysteine and pyrrolysine insertion (encoded by UGA and UAG, respectively) in competition with translation termination. Ambiguous meaning of CUG in coding for serine and leucine is also known. However, a recent study revealed that codons in any position within the open reading frame can serve a dual function and that a change in codon meaning can be achieved by availability of a specific type of RNA stem-loop structure in the 3'-untranslated region. Thus, duality of codon function is a more widely used feature of the genetic code than previously known, and this observation raises the possibility that additional recoding events and additional novel features have evolved in the genetic code.
遗传密码的发现为现代分子生物学的基本基础之一提供了依据。大多数生物体使用相同的遗传语言，但也有充分记录的变异，代表特定生物体群体（如纤毛虫和酵母）或细胞器（如质体和线粒体）内的密码子重新分配。此外，在翻译起始时 AUG 的使用以及甲硫氨酸插入内部蛋白质位置以及硒代半胱氨酸和吡咯赖氨酸插入（分别由 UGA 和 UAG 编码）与翻译终止竞争中，密码子功能的双重性是已知的。CUG 在编码丝氨酸和亮氨酸时的含义不明确也为人所知。然而，最近的一项研究表明，开放阅读框内任何位置的密码子都可以具有双重功能，并且通过在 3'非翻译区中存在特定类型的 RNA 茎环结构，可以实现密码子含义的改变。因此，密码子功能的双重性是遗传密码中比以前已知的更为广泛使用的特征，这一观察结果提出了在遗传密码中可能已经进化出额外的重编码事件和其他新特征的可能性。
