DNA: Difference between revisions
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==Transposable Elements== | ==Transposable Elements== | ||
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A [https://en.wikipedia.org/wiki/Transposable_element transposable element] (TE) or transposon is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Many TEs contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes. | A [https://en.wikipedia.org/wiki/Transposable_element transposable element] (TE) or transposon is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Many TEs contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes. | ||
===Retrotransposons=== | ===Retrotransposons=== | ||
[https://en.wikipedia.org/wiki/Retrotransposon Retrotransposons] also called transposons via RNA intermediate are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. These DNA sequences use a "copy-and-paste" mechanism, whereby they are first transcribed into RNA, then converted back into identical DNA sequences using reverse transcription, and these sequences are then inserted into the genome at target sites. | [https://en.wikipedia.org/wiki/Retrotransposon Retrotransposons] also called transposons via RNA intermediate are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. These DNA sequences use a "copy-and-paste" mechanism, whereby they are first transcribed into RNA, then converted back into identical DNA sequences using reverse transcription, and these sequences are then inserted into the genome at target sites. | ||
===DNA Transposons=== | ===DNA Transposons=== | ||
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===Short Interspersed Nuclear Elements === | ===Short Interspersed Nuclear Elements === | ||
[https://en.wikipedia.org/wiki/Short_interspersed_nuclear_element Short Interspersed Nuclear Elements] (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are 50-500 base pairs long. 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. | [https://en.wikipedia.org/wiki/Short_interspersed_nuclear_element Short Interspersed Nuclear Elements] (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are 50-500 base pairs long. 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. | ||
==Pseudogenes== | |||
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[https://en.wikipedia.org/wiki/Pseudogene Pseudogenes] are segments of DNA that are related to real genes. Pseudogenes have lost at least some functionality, relative to the complete gene, in cellular gene expression or protein-coding ability. Pseudogenes often result from the accumulation of multiple mutations within a gene whose product is not required for the survival of the organism, but can also be caused by genomic copy number variation (CNV) where segments of 1+ kb are duplicated or deleted. Although not fully functional, pseudogenes may be functional, similar to other kinds of noncoding DNA, which can perform regulatory functions. The "pseudo" in "pseudogene" implies a variation in sequence relative to the parent coding gene, but does not necessarily indicate pseudo-function. Despite being non-coding, many pseudogenes have important roles in normal physiology and abnormal pathology. | |||
Revision as of 07:28, 11 November 2017
This page is about DNA and interesting genomic phenomena.
Transposable Elements
A transposable element (TE) or transposon is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Many TEs contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes.
Retrotransposons
Retrotransposons also called transposons via RNA intermediate are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. These DNA sequences use a "copy-and-paste" mechanism, whereby they are first transcribed into RNA, then converted back into identical DNA sequences using reverse transcription, and these sequences are then inserted into the genome at target sites.
DNA Transposons
DNA Transposons (aka Class II elements) are a group of transposable elements that can move in the DNA of an organism via a single- or double-stranded DNA intermediate. There are autonomous, as well as nonautonomous DNA transposons. The latter use the enzymatic machinery of the former for their amplification in a genome. It is estimated, that there are around 300,000 copies of DNA transposon fossils in the human genome and they make up around 3% of it.
Alu element
An Alu element is a short stretch of DNA originally characterized by the action of the Arthrobacter luteus (Alu) restriction endonuclease.[1] Alu elements are the most abundant transposable elements, containing over one million copies dispersed throughout the human genome.[2] They are derived from the small cytoplasmic 7SL RNA, a component of the signal recognition particle.
Short Interspersed Nuclear Elements
Short Interspersed Nuclear Elements (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are 50-500 base pairs long. 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.
Pseudogenes
Pseudogenes are segments of DNA that are related to real genes. Pseudogenes have lost at least some functionality, relative to the complete gene, in cellular gene expression or protein-coding ability. Pseudogenes often result from the accumulation of multiple mutations within a gene whose product is not required for the survival of the organism, but can also be caused by genomic copy number variation (CNV) where segments of 1+ kb are duplicated or deleted. Although not fully functional, pseudogenes may be functional, similar to other kinds of noncoding DNA, which can perform regulatory functions. The "pseudo" in "pseudogene" implies a variation in sequence relative to the parent coding gene, but does not necessarily indicate pseudo-function. Despite being non-coding, many pseudogenes have important roles in normal physiology and abnormal pathology.