The origin of life is a long-standing mystery which has puzzled many people. This mystery possesses not only philosophical, but also important biological significance. In order to unveil this mystery, first we can gain insight fiom the LUCA, that is, the Last Universal Common Ancestor, a hypothetical common ancestor to all the living organisms existing today. In this thesis, I have demonstrated how transfer RNAs, a group of short RNA sequences which are usually regarded as lack of evolutionary information, can be used to construct the universal tree of life. From the study of the universal tree of life, we proposed that the location of LUCA is at the branches in this tree of life which leads to two archaea, Methanopyrus kandleri and Aeropyrum pernix. The tree building with transfer RNA...[ Read more ]

The origin of life is a long-standing mystery which has puzzled many people. This mystery possesses not only philosophical, but also important biological significance. In order to unveil this mystery, first we can gain insight fiom the LUCA, that is, the Last Universal Common Ancestor, a hypothetical common ancestor to all the living organisms existing today. In this thesis, I have demonstrated how transfer RNAs, a group of short RNA sequences which are usually regarded as lack of evolutionary information, can be used to construct the universal tree of life. From the study of the universal tree of life, we proposed that the location of LUCA is at the branches in this tree of life which leads to two archaea, Methanopyrus kandleri and Aeropyrum pernix. The tree building with transfer RNA apart, the studies of aminoacyl-tRNA synthetase and anticodon usage showed further evidence that all pointed to Methanopyrus kandleri as the currently existing organism which resembles the LUCA most. Therefore further studies on this archaea may shed new light on the origin of life.