RNA-based evolution

RNA-based evolution is a

Role of RNA in conventional evolution

In accordance with the

Research within the past decade has shown that strands of RNA are not merely transcribed from regions of DNA and translated into proteins. Rather RNA has retained some of its former independence from DNA and is subject to a network of processing events that alter the protein expression from that bounded by just the genomic DNA.[9] Processing of RNA influences protein expression by managing the transcription of DNA sequences, the stability of RNA, and the translation of messenger RNA.

Alternative splicing

Splicing is the process by which non-coding regions of RNA are removed. The number and combination of splicing events varies greatly based on differences in transcript sequence and environmental factors. Variation in phenotype caused by alternative splicing is best seen in the sex determination of D. melanogaster. The Tra gene, determinant of sex, in male flies becomes truncated as splicing events fail to remove a stop codon that controls the length of the RNA molecule. In others the stop signal is retained within the final RNA molecule and a functional Tra protein is produced resulting in the female phenotype.^[10] Thus, alternative RNA splicing events allow differential phenotypes, regardless of the identity of the coding DNA sequence.

RNA stability

Phenotype may also be determined by the number of RNA molecules, as more RNA transcripts lead to a greater expression of protein. Short tails of repetitive nucleic acids are often added to the ends of RNA molecules in order to prevent degradation, effectively increasing the number of RNA strands able to be translated into protein.^[11] During mammalian liver regeneration RNA molecules of growth factors increase in number due to the addition of signaling tails.^[12] With more transcripts present the growth factors are produced at a higher rate, aiding the rebuilding process of the organ.

RNA silencing

Silencing of RNA occurs when double stranded RNA molecules are processed by a series of enzymatic reactions, resulting in RNA fragments that degrade complementary RNA sequences.^[13][14] By degrading transcripts, a lower amount of protein products are translated and the phenotype is altered by yet another RNA processing event.

RNA and Protein

In Earth's early developmental history RNA was the primary substance of life. RNA served as a blueprint for genetic material and was the catalyst to multiply said blueprint. Currently RNA acts by forming proteins. protein enzymes carry out catalytic reactions. RNAs are critical in gene expression and that gene expression depends on mRNA, rRNA, and tRNA.^[15] There is a relationship between protein and RNAs. This relationship could suggest that there is a mutual transfer of energy or information.^[16] In vitro RNA selection experiments have produced RNA that bind tightly to amino acids. It has been shown that the amino acids recognized by the RNA nucleotide sequences had a disproportionately high frequency of codons for said amino acids. There is a possibility that the direct association of amino acids containing specific RNA sequences yielded a limited genetic code.^[17]

Evolutionary mechanism

Most RNA processing events work in concert with one another and produce networks of regulating processes that allow a greater variety of proteins to be expressed than those strictly directed by the genome.

• RNA world

References