Molecular evolution

Molecular evolution is a process of change in a sequence composition of cellular molecules such(a) as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology as alive as population genetics to explain patterns in these changes. Major topics in molecular evolution concern the rates in addition to impacts of single nucleotide changes, neutral evolution vs. natural selection, origins of new genes, the genetic mark of complex traits, the genetic basis of speciation, evolution of development, and ways that evolutionary forces influence genomic and phenotypic changes.

Origins of new genes

New genes arise from several different genetic mechanisms including gene duplication, de novo origination, retrotransposition, chimeric gene formation, recruitment of non-coding sequence, and gene truncation.

Gene duplication initially leads to redundancy. However, duplicated gene sequences can mutate to imposing new functions or specialize so that the new gene performs a subset of the original ancestral functions. In addition to duplicating whole genes, sometimes only a domain or part of a protein is duplicated so that the resulting gene is an elongated relation of the parental gene.

Retrotransposition creates new genes by copying mRNA to DNA and inserting it into the genome. Retrogenes often insert into new genomic locations, and often creation new expression patterns and functions.

Chimeric genes construct when duplication, deletion, or incomplete retrotransposition combine portions of two different developing sequences to make-up a novel gene sequence. Chimeras often cause regulatory revise and can shuffle protein domains to produce novel adaptive functions.

De novo gene birth can also administer rise to new genes from before non-coding DNA. For instance, Levine and colleagues filed the origin of five new genes in the D. melanogaster genome from noncoding DNA. Similar de novo origin of genes has been also submitted in other organisms such(a) as yeast, rice and humans. De novo genes may evolve from transcripts that are already expressed at low levels. Mutation of a stop codon to acodon or a frameshift may cause an extended protein that includes a previously non-coding sequence. The array of novel genes from scratch typically can non occur within genomic regions of high gene density. The essential events for de novo array of genes is recombination/mutation which includes insertions, deletions, and inversions. These events are tolerated if the consequence of these genetic events does non interfere in cellular activities. near genomes comprise prophages wherein genetic modifications do not, in general, affect the host genome propagation. Hence, there is higher probability of genetic modifications, in regions such as prophages, which is proportional to the probability of de novo formation of genes.

De novo evolution of genes can also be simulated in the laboratory. For example, semi-random gene sequences can be selected for specific functions. More specifically, they selected sequences from a the treasure of knowledge that could complement a gene deletion in E. coli. The deleted gene encodes ferric enterobactin esterase Fes, which releases iron from an iron chelator, enterobactin. While Fes is a 400 amino acid protein, the newly selected gene was only 100 amino acids in length and unrelated in sequence to Fes.