Abstract
The RNA world hypothesis on the origin of life is generally considered as the key to solve the “chicken and egg dilemma” concerning the evolution of genes and proteins as observed in the modern organisms. This hypothesis, however, contains several serious weak points. We have a counterproposal called [GADV]-protein world hypothesis, abbreviated as GADV hypothesis, in which we have suggested that life originated from a [GADV]-protein world, which comprised proteins composed of four amino acids: Gly [G], Ala [A], Asp [D], and Val [V]. A new concept “pseudo-replication” is crucial for the description of the emergence of life. The new hypothesis not only plausibly explains how life originated from the initial chaotic protein world, but also how genes, genetic code, and proteins co-evolved.
Highlights
While genetic information in the form of DNA base sequences or codon sequences is transferred from a parent to progeny cells through DNA replication, the same information is transformed into mRNA and into amino acid sequence of proteins, according to the genetic code specifications (Figure 1)
The RNA world hypothesis is widely accepted at present, but this hypothesis cannot explain how the first gene and the most primitive genetic code emerged on the primitive Earth
Hypothesis can plausibly explain how the most primitive genetic code was introduced on the primitive Earth and how the first gene encoding the first protein was created, and it suggests how the
Summary
While genetic information in the form of DNA base sequences or codon sequences is transferred from a parent to progeny cells through DNA replication, the same information is transformed into mRNA and into amino acid sequence of proteins, according to the genetic code specifications (Figure 1). About 25 years ago, RNA enzymes with some catalytic activities were discovered; they are named ribozymes [1,2] This discovery suggests that RNA might possess genetic function and catalytic function. Based on this interpretation, Gilbert proposed his RNA world hypothesis of the origin of life [3]. Gilbert proposed his RNA world hypothesis of the origin of life [3] He assumed that RNA had been multiplied and diversified by self-replication to form the RNA world, and that genetic function and catalytic function of RNA were transferred to DNA and proteins, respectively [Figure 2 (a)], resulting in the emergence of life from the RNA world. The discovery of ribozymes gave a motivation for introduction of the new concept or RNA self-replication [Figure 2 (b)]
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