RNA world hypothesis.Gilbert Step 2: Step 1 Step 3: RNA self-replicates RNA forms from RNA catalyses (via ribozymes) InorganIc sources protein synthesis 一 Step 4: Membrane formation changes internal chemistr DNA RNA Proteins Genetic information Messenger Catalytic function Genetic information Catalytic functi
RNA world hypothesis Genetic information Messenger Catalytic function DNA RNA Proteins Genetic information Catalytic function W. Gilbert
Science.2009Fb27;323(5918):122932 Self-Sustained Replication of an RNA Enzyme Tracey A Lincoln and Gerald f. Joyce* An RNa enzyme that catalyzes the rna-templated joining of rna was converted to a format whereby two enzymes catalyze each other s synthesis from a total of four oligonucleotide substrates. these cross-replicating RNA enzymes undergo self-sustained exponential amplification in the absence of proteins or other biological materials. Amplification occurs with a doubling time of about 1 hour and can be continued indefinitely. Populations of various cross-replicating enzymes were constructed and allowed to compete for a common pool of substrates, during which recombinant replicators arose and grew to dominate the population. These replicating RNa enzymes can serve as an experimental model of a genetic system Many such model systems could be constructed allowing different selective outcomes to be related to the underlying properties of the genetic system
Science. 2009 Feb 27;323(5918):1229-32
G-C S-OQUUCAUGU GGUUGANGAAUgAGacc-gcaacuuas cuA电ea- CCAGAG-UUUdA,GUUag UouugAAcos E RNA分子可以自我进化! AuuGuucUA UUCA “=:“=1 UCAU GAAU CAUU “4°18 E10 4-8E11 UUUC =8E12 CAUA A AAAG UCA CAU uA§8 Cross-replicating RNA enzymes
Cross-replicating RNA enzymes. RNA分子可以自我进化！
基因组的起源 人们推测基因组的起源可能是 最初的DNA基因组由许多分散的分子组成,每一个指 令单个蛋白质,相当于一个基因。这些基因彼此连接成 染色体。 由于组成了含更多基因的染色体,在细胞分裂时基 因的分配要比分散的类型更加有效而方便,在竟争中占 有优势。 随着早期基因组的多次进化,彼此连接的基因所具 有的不同功能也随之发展与演变。 这一假说还无法提供证据
基因组的起源 人们推测基因组的起源可能是: 最初的DNA基因组由许多分散的分子组成，每一个指 令单个蛋白质，相当于一个基因。这些基因彼此连接成 染色体。 由于组成了含更多基因的染色体，在细胞分裂时基 因的分配要比分散的类型更加有效而方便，在竟争中占 有优势。 随着早期基因组的多次进化，彼此连接的基因所具 有的不同功能也随之发展与演变。 这一假说还无法提供证据
生命之根在哪? 细菌 古细菌 真核生物 生命三界 (Carl Woese) 共同先
生 命 三 界 生命之根在哪? (Carl Woese) ？