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An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word intron is derived from the term intragenic region, i.e. a region inside a gene. The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons.
RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns and splicing back together exons. For nuclear-encoded genes, splicing occurs in the nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translated into protein. For many eukaryotic introns, splicing occurs in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs). There exist self-splicing introns, that is, ribozymes that can catalyze their own excision from their parent RNA molecule. The process of transcription, splicing and translation is called gene expression, the central dogma of molecular biology.
The Selfish Gene is a 1976 book on evolution by the ethologist Richard Dawkins, in which the author builds upon the principal theory of George C. Williams's Adaptation and Natural Selection (1966). Dawkins uses the term "selfish gene" as a way of expressing the gene-centred view of evolution, popularising ideas developed during the 1960s by W. D. Hamilton and others. From the gene-centred view, it follows that the more two individuals are genetically related, the more sense it makes for them to behave cooperatively with each other.
Selfish genetic elements are genetic segments that can enhance their own transmission at the expense of other genes in the genome, even if this has no positive or a net negative effect on organismal fitness. Genomes have traditionally been viewed as cohesive units, with genes acting together to improve the fitness of the organism. However, when genes have some control over their own transmission, the rules can change, and so just like all social groups, genomes are vulnerable to selfish behaviour by their parts.
Biological determinism, also known as genetic determinism, is the belief that human behaviour is directly controlled by an individual's genes or some component of their physiology, generally at the expense of the role of the environment, whether in embryonic development or in learning. Genetic reductionism is a similar concept, but it is distinct from genetic determinism in that the former refers to the level of understanding, while the latter refers to the supposedly causal role of genes. Biological determinism has been associated with movements in science and society including eugenics, scientific racism, and the debates around the heritability of IQ, the basis of sexual orientation, and sociobiology.
Evolutionary developmental biology is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved.
William Donald Hamilton was a British evolutionary biologist, recognised as one of the most significant evolutionary theorists of the 20th century.
Molecular evolution is the process of change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genetics to explain patterns in these changes. Major topics in molecular evolution concern the rates and impacts of single nucleotide changes, neutral evolution vs. natural selection, origins of new genes, the genetic nature of complex traits, the genetic basis of speciation, evolution of development, and ways that evolutionary forces influence genomic and phenotypic changes.
Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene.
Antisense RNA (asRNA), also referred to as antisense transcript, natural antisense transcript (NAT) or antisense oligonucleotide, is a single stranded RNA that is complementary to a protein coding messenger RNA (mRNA) with which it hybridizes, and thereby blocks its translation into protein. asRNAs have been found in both prokaryotes and eukaryotes, and can be classified into short and long non-coding RNAs (ncRNAs). The primary function of asRNA is regulating gene expression. asRNAs may also be produced synthetically and have found wide spread use as research tools for gene knockdown. They may also have therapeutic applications.
With gene defined as "not just one single physical bit of DNA [but] all replicas of a particular bit of DNA distributed throughout the world", the gene-centered view of evolution, gene's eye view, gene selection theory, or selfish gene theory holds that adaptive evolution occurs through the differential survival of competing genes, increasing the allele frequency of those alleles whose phenotypic trait effects successfully promote their own propagation. The proponents of this viewpoint argue that, since heritable information is passed from generation to generation almost exclusively by DNA, natural selection and evolution are best considered from the perspective of genes.
Intragenomic conflict refers to the evolutionary phenomenon where genes have phenotypic effects that promote their own transmission in detriment of the transmission of other genes that reside in the same genome. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects cause their transmission to new organisms, and most genes achieve this by cooperating with other genes in the same genome to build an organism capable of reproducing and/or helping kin to reproduce. The assumption of the prevalence of intragenomic cooperation underlies the organism-centered concept of inclusive fitness. However, conflict among genes in the same genome may arise both in events related to reproduction and altruism.
Cis-regulatory elements (CREs) or Cis-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morphogenesis, the development of anatomy, and other aspects of embryonic development, studied in evolutionary developmental biology.
Denis Noble is a British biologist who held the Burdon Sanderson Chair of Cardiovascular Physiology at the University of Oxford from 1984 to 2004 and was appointed Professor Emeritus and co-Director of Computational Physiology. He is one of the pioneers of systems biology and developed the first viable mathematical model of the working heart in 1960.
A gene family is a set of homologous genes within one organism. A gene cluster is a group of two or more genes found within an organism's DNA that encode similar polypeptides, or proteins, which collectively share a generalized function and are often located within a few thousand base pairs of each other. The size of gene clusters can vary significantly, from a few genes to several hundred genes. Portions of the DNA sequence of each gene within a gene cluster are found to be identical; however, the resulting protein of each gene is distinctive from the resulting protein of another gene within the cluster. Genes found in a gene cluster may be observed near one another on the same chromosome or on different, but homologous chromosomes. An example of a gene cluster is the Hox gene, which is made up of eight genes and is part of the Homeobox gene family.
Trans-regulatory elements (TRE) are DNA sequences encoding upstream regulators, which may modify or regulate the expression of distant genes. Trans-acting factors interact with cis-regulatory elements to regulate gene expression. TRE mediates expression profiles of a large number of genes via trans-acting factors. While TRE mutations affect gene expression, it is also one of the main driving factors for evolutionary divergence in gene expression.
The one gene–one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway. The concept was proposed by George Beadle and Edward Tatum in an influential 1941 paper on genetic mutations in the mold Neurospora crassa, and subsequently was dubbed the "one gene–one enzyme hypothesis" by their collaborator Norman Horowitz. In 2004, Horowitz reminisced that "these experiments founded the science of what Beadle and Tatum called 'biochemical genetics.' In actuality they proved to be the opening gun in what became molecular genetics and all the developments that have followed from that." The development of the one gene–one enzyme hypothesis is often considered the first significant result in what came to be called molecular biology. Although it has been extremely influential, the hypothesis was recognized soon after its proposal to be an oversimplification. Even the subsequent reformulation of the "one gene–one polypeptide" hypothesis is now considered too simple to describe the relationship between genes and proteins.
Expression quantitative trait loci (eQTLs) are genomic loci that explain variation in expression levels of mRNAs.
Albert Erives is a developmental geneticist who studies transcriptional enhancers underlying animal development and diseases of development (cancers). Erives also proposed the pacRNA model for the dual origin of the genetic code and universal homochirality. He is known for work at the intersection of genetics, evolution, developmental biology, and gene regulation. He has worked at the California Institute of Technology, University of California, Berkeley, and Dartmouth College, and is an associate professor at the University of Iowa.
An outron is a nucleotide sequence at the 5' end of the primary transcript of a gene that is removed by a special form of RNA splicing during maturation of the final RNA product. Whereas intron sequences are located inside the gene, outron sequences lie outside the gene.
References
- ↑ Dawkins R (1989). The selfish gene (New ed.). Oxford: Oxford University Press. ISBN 0-19-217773-7. OCLC 20012195.
- ↑ Bateman JR, Johnson JE, Locke MN (August 2012). "Comparing enhancer action in cis and in trans". Genetics. 191 (4): 1143–1155. doi:10.1534/genetics.112.140954. PMC 3415998 . PMID 22649083.
- 1 2 Piast RW (June 2019). "Shannon's information, Bernal's biopoiesis and Bernoulli distribution as pillars for building a definition of life". Journal of Theoretical Biology. 470: 101–107. doi:10.1016/j.jtbi.2019.03.009. PMID 30876803. S2CID 80625250.