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Retroposon
Retroposons are repetitive DNA fragments which are inserted into chromosomes after they had been reverse transcribed from any RNA molecule. Difference between retroposons and retrotransposons In contrast to retrotransposons, retroposons never encode reverse transcriptase (RT) (but see below). Therefore, they are non-autonomous elements with regard to transposition activity (as opposed to transposons). Non-long terminal repeat (LTR) retrotransposons such as the human LINE1 elements are sometimes falsely referred to as retroposons. However, this depends on the author. For example, Howard Temin published the following definition: Retroposons encode RT but are devoid of long terminal repeats (LTRs), for example long interspersed elements (LINEs). Retrotransposons also feature LTRs and retroviruses, in addition, are packaged as viral particles (virions). Retrosequences are non-autonomous elements devoid of RT. They are retroposed with the aid of the machinery of autonomous element ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transposon
A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transposition often results in duplication of the same genetic material. Barbara McClintock's discovery of them earned her a Nobel Prize in 1983. Its importance in personalized medicine is becoming increasingly relevant, as well as gaining more attention in data analytics given the difficulty of analysis in very high dimensional spaces. Transposable elements make up a large fraction of the genome and are responsible for much of the C-value, mass of DNA in a eukaryotic cell. Although TEs are selfish genetic elements, many are important in genome function and evolution. Transposons are also very useful to researchers as a means to alter DNA inside a living organism. There are at least two classes of TEs: Class I TEs or retrotransposons generally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transposition (genetics)
A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transposition often results in duplication of the same genetic material. Barbara McClintock's discovery of them earned her a Nobel Prize in 1983. Its importance in personalized medicine is becoming increasingly relevant, as well as gaining more attention in data analytics given the difficulty of analysis in very high dimensional spaces. Transposable elements make up a large fraction of the genome and are responsible for much of the mass of DNA in a eukaryotic cell. Although TEs are selfish genetic elements, many are important in genome function and evolution. Transposons are also very useful to researchers as a means to alter DNA inside a living organism. There are at least two classes of TEs: Class I TEs or retrotransposons generally functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudogene
Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by Reverse transcriptase, reverse transcription of an mRNA transcript. Pseudogenes are usually identified when genome sequence analysis finds gene-like sequences that lack regulatory sequences needed for Transcription (biology), transcription or Translation (biology), translation, or whose coding sequences are obviously defective due to Frameshift mutation, frameshifts or premature stop codons. Most non-bacterial genomes contain many pseudogenes, often as many as functional genes. This is not surprising, since various biological processes are expected to accidentally create pseudogenes, and there are no specialized mechanisms to remove them from genomes. Eventually pseudogenes may be deleted from their genomes by chance DNA replication or DNA repair errors, or they may accumulate so many mutational cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetic Tree Of Marsupials Derived From Retroposon Data - Journal
In biology, phylogenetics (; from Greek language, Greek wikt:φυλή, φυλή/wikt:φῦλον, φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by Computational phylogenetics, phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, Protein, protein Amino acid, amino acid sequences, or Morphology (biology), morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. The tips of a phylogenetic tree can be living taxa or fossils, and represent the "end" or the present time in an evolutionary lineage. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the tree. An un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retroviruses
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus ''retro'' (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. Although retroviruses have different subfamilies, they have three basic groups: the oncoretroviruses (oncogenic retroviruses), the lentiviruses (slow retroviruses) and the spumaviruses (foamy viruses). The oncoretroviruses are able to cause cancer in some species, the lentiviruse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intron
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 notion of the cistron .e., gene... must be replaced by that of a transcription unit containing regions which will be lost from the mature messenger – which I suggest we call introns (for intragenic regions) – alternating with regions which will be expressed – exons." (Gilbert 1978) 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. Introns are found in the genes of most organisms and many viruses and they can be located in both protein-coding genes and genes that function as RNA (noncoding genes). There are four main types of introns: tRNA introns, group I introns, group II introns, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proto-oncogene Tyrosine-protein Kinase Src
Proto-oncogene tyrosine-protein kinase Src, also known as proto-oncogene c-Src, or simply c-Src (cellular Src; pronounced "sarc", as it is short for sarcoma), is a non-receptor tyrosine kinase protein that in humans is encoded by the ''SRC'' gene. It belongs to a family of Src family kinases and is similar to the v-Src (viral Src) gene of Rous sarcoma virus. It includes an SH2 domain, an SH3 domain and a tyrosine kinase domain. Two transcript variants encoding the same protein have been found for this gene. c-Src phosphorylates specific tyrosine residues in other tyrosine kinases. It plays a role in the regulation of embryonic development and cell growth. An elevated level of activity of c-Src is suggested to be linked to cancer progression by promoting other signals. Mutations in c-Src could be involved in the malignant progression of colon cancer. c-Src should not be confused with CSK (C-terminal Src kinase), an enzyme that phosphorylates c-Src at its C-terminus and provides n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. Gene duplications can arise as products of several types of errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements. Common sources of gene duplications include ectopic recombination, retrotransposition event, aneuploidy, polyploidy, and replication slippage. Mechanisms of duplication Ectopic recombination Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The chance of it happening is a function of the degree of sharing of repetitive elements between two chromosomes. The products of this recombination are a duplication at the site of the exchange and a reciprocal deletion. Ectopic recombination is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Short Interspersed Nuclear Element
Short interspersed nuclear elements (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are about 100 to 700 base pairs in length. They are a class of retrotransposons, DNA elements that amplify themselves throughout eukaryotic genomes, often through RNA intermediates. SINEs compose about 13% of the mammalian genome. The internal regions of SINEs originate from tRNA and remain highly conserved, suggesting positive pressure to preserve structure and function of SINEs. While SINEs are present in many species of vertebrates and invertebrates, SINEs are often lineage specific, making them useful markers of divergent evolution between species. Copy number variation and mutations in the SINE sequence make it possible to construct phylogenies based on differences in SINEs between species. SINEs are also implicated in certain types of genetic disease in humans and other eukaryotes. In essence, short interspersed nuclear elements are genetic parasites which have evolv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long Terminal Repeat
A long terminal repeat (LTR) is a pair of identical sequences of DNA, several hundred base pairs long, which occur in eukaryotic genomes on either end of a series of genes or pseudogenes that form a retrotransposon or an endogenous retrovirus or a retroviral provirus. All retroviral genomes are flanked by LTRs, while there are some retrotransposons without LTRs. Typically, an element flanked by a pair of LTRs will encode a reverse transcriptase and an integrase, allowing the element to be copied and inserted at a different location of the genome. Copies of such an LTR-flanked element can often be found hundreds or thousands of times in a genome. LTR retrotransposons comprise about 8% of the human genome. The first LTR sequences were found by A.P. Czernilofsky and J. Shine in 1977 and 1980. Transcription The LTR-flanked sequences are partially transcribed into an RNA intermediate, followed by reverse transcription into complementary DNA (cDNA) and ultimately dsDNA (double-stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long Interspersed Nuclear Element
Long interspersed nuclear elements (LINEs) (also known as long interspersed nucleotide elements or long interspersed elements) are a group of non-LTR (long terminal repeat) retrotransposons that are widespread in the genome of many eukaryotes. They make up around 21.1% of the human genome. LINEs make up a family of transposons, where each LINE is about 7,000 base pairs long. LINEs are transcribed into mRNA and translated into protein that acts as a reverse transcriptase. The reverse transcriptase makes a DNA copy of the LINE RNA that can be integrated into the genome at a new site. The only abundant LINE in humans is LINE1. The human genome contains an estimated 100,000 truncated and 4,000 full-length LINE-1 elements. Due to the accumulation of random mutations, the sequence of many LINEs has degenerated to the extent that they are no longer transcribed or translated. Comparisons of LINE DNA sequences can be used to date transposon insertion in the genome. History of discovery ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
