Pseudo-replication of [GADV]-proteins and origin of life

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.

Keywords: GADV hypothesis; [GADV]-protein world; origin of life; pseudo-replication.

Figure 1.

The role of genetic code playing in the fundamental life system of modern organisms.

Figure 2.

(a) According to the RNA world hypothesis, the genetic function and the catalytic function carried by RNA were transferred to DNA and proteins, respectively. (b) A motivation and an instrumental concept were introduced for proposing the RNA world hypothesis on the origin of life.

Figure 3.

GC-NSF(a) hypothesis for creation of new original ancestor genes (NOA genes), suggesting that NOA genes would be created from non-stop frames on antisense strands of GC-rich genes [GC-NSF(a)] as prescribed by the universal genetic code after gene duplication. On the other hand, homologous genes are created from sense sequences, regardless of GC content.

Figure 4.

GNC-SNS hypothesis on the origin and evolutionary pathway of the genetic code, suggesting that the universal genetic code originated from GNC primeval genetic code through SNS primitive genetic code.

Figure 5.

(a) [GADV]-protein world hypothesis (GADV hypothesis) about the origin of life: Life originated from the [GADV]-protein world, which was created by pseudo-replication of [GADV]-proteins i.e., random polymerization of [GADV]-amino acids in a specific amino acid composition (a protein 0^th-order structure). Life emerged from the [GADV]-protein world through generating GNC primeval genetic code. (b) Development of [GADV]-protein world hypothesis on the origin of life. Solid lines and a dotted line show the history and time flow, respectively.

Figure 5.

(a) [GADV]-protein world hypothesis (GADV hypothesis) about the origin of life: Life originated from the [GADV]-protein world, which was created by pseudo-replication of [GADV]-proteins i.e., random polymerization of [GADV]-amino acids in a specific amino acid composition (a protein 0^th-order structure). Life emerged from the [GADV]-protein world through generating GNC primeval genetic code. (b) Development of [GADV]-protein world hypothesis on the origin of life. Solid lines and a dotted line show the history and time flow, respectively.

Figure 6.

(a) Formation processes of the life system (chicken and egg relationship between DNA and proteins) viewed from the GADV hypothesis. (b) The motivation and the new instrumental concept for the GADV hypothesis on the origin of life.

Figure 7.

Two routes for creation of new genes. (a) While new (GNC)_n genes homologous with parental gene were produced from GNC codon sequences on the sense strand (route 1), NOA genes were created from GNC codon sequences on the anti-sense strands (route 2). (b) Two routes 1 and 2 similar to those as shown in (a) would be utilized for creation of new genes, when necessary, always after creation of the first double-stranded (GNC)_n gene.

Figure 7.

Two routes for creation of new genes. (a) While new (GNC)_n genes homologous with parental gene were produced from GNC codon sequences on the sense strand (route 1), NOA genes were created from GNC codon sequences on the anti-sense strands (route 2). (b) Two routes 1 and 2 similar to those as shown in (a) would be utilized for creation of new genes, when necessary, always after creation of the first double-stranded (GNC)_n gene.

Figure 8.

A possible evolutionary pathway of the life system, which comprised genes, genetic code (codons for amino acids), and proteins, and originated from the [GADV]-protein world. Solid arrows, dotted arrows and a broken arrow indicate directions of evolutionary pathways of the life system, the expression of genetic information, and the time flow, respectively.