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D-loop
In molecular biology, a displacement loop or D-loop is a DNA structure where the two strands of a double-stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA. An R-loop is similar to a D-loop, but in this case the third strand is RNA rather than DNA. The third strand has a base sequence which is complementary to one of the main strands and pairs with it, thus displacing the other complementary main strand in the region. Within that region the structure is thus a form of triple-stranded DNA. A diagram in the paper introducing the term illustrated the D-loop with a shape resembling a capital "D", where the displaced strand formed the loop of the "D". D-loops occur in a number of particular situations, including in DNA repair, in telomeres, and as a semi-stable structure in mitochondrial circular DNA molecules. In mitochondria Researchers at Caltech discovered in 1971 that the circular mitochondrial DNA from growing cells included a sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologous Recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may be also RNA in viruses). Homologous recombination is widely used by cells to accurately DNA repair harmful breaks that occur on both strands of DNA, known as double-strand breaks (DSB), in a process called homologous recombinational repair (HRR). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species of bacteria and viruses. Horizon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MtDNA Control Region
The mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. This region controls RNA and DNA synthesis. It is the most polymorphic region of the human mtDNA genome, with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%. Despite this variability, an RNA transcript from this region has a conserved secondary structure (''pictured'') which has been found to be under selective pressure. The mtDNA control region contains the origin of replication of one strand, and the origin of transcription for both strands. There is also an open reading frame thought to code for 7s ribosomal RNA in humans but not in mice or cows, where it has been deleted. Distinction from D-loop The control region and mtDNA D-loop are sometimes used synonymously in the literature; specifically the control region includes the D-loop along with adjacent transcription promoter regions. For this reason, the control reg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shelterin
Shelterin (also called telosome) is a protein complex known to protect telomeres in many eukaryotes from DNA repair mechanisms, as well as to regulate telomerase activity. In mammals and other vertebrates, telomeric DNA consists of repeating double-stranded 5'-TTAGGG-3' (G-strand) sequences (2-15 Base pair#Length measurements, kilobases in humans) along with the 3'-AATCCC-5' (C-strand) complement, ending with a 50-400 nucleotide 3' (G-strand) overhang. Much of the final double-stranded portion of the telomere forms a T-loop (Telomere-loop) that is invaded by the 3' (G-strand) overhang to form a small D-loop (Displacement-loop). The absence of shelterin causes telomere uncapping and thereby activates damage-signaling pathways that may lead to non-homologous end joining (NHEJ), homology directed repair (HDR), end-to-end fusions, genomic instability, senescence, or apoptosis. Subunits Shelterin has six subunits: TRF1, TRF2, POT1, RAP1, TIN2, and TPP1. They can ope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triple-stranded DNA
Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds. Structure Examples of triple-stranded DNA have been found in natural sources with the required structural elements, for example in Satellite DNA. Hoogsteen base pairing A thymine (T) nucleobase can bind to a Watson–Crick base-pairing of T-A by forming a Hoogsteen hydrogen bond. The thymine hydrogen bonds with the adenosine (A) of the original double-stranded DNA to create a T-A*T base-triplet. Intermolecular and intramolecular interactions There are two classes of triplex DNA: intermolecular and intramolecular formations. An intermolecular triplex refers to triplex formation between a duplex and a different (third) strand of DNA. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-loop
An R-loop is a three-stranded nucleic acid structure, composed of a DNA: RNA hybrid and the associated non-template single-stranded DNA. R-loops may be formed in a variety of circumstances, and may be tolerated or cleared by cellular components. The term "R-loop" was given to reflect the similarity of these structures to D-loops; the "R" in this case represents the involvement of an RNA moiety. In the laboratory, R-loops may also be created by the hybridization of mature mRNA with double-stranded DNA under conditions favoring the formation of a DNA-RNA hybrid; in this case, the intron regions (which have been spliced out of the mRNA) form single-stranded DNA loops, as they cannot hybridize with complementary sequence in the mRNA. History R-looping was first described in 1976. Independent R-looping studies from the laboratories of Richard J. Roberts and Phillip A. Sharp showed that protein coding adenovirus genes contained DNA sequences that were not present in the mature mR ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages (interstrand crosslinks or ICLs). This can eventually lead to malign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telomere
A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature most commonly found in eukaryotes. In most, if not all species possessing them, they protect the terminal regions of chromosomal DNA from progressive degradation and ensure the integrity of linear chromosomes by preventing DNA repair systems from mistaking the very ends of the DNA strand for a double-strand break. Discovery In the early 1970s, Soviet theorist Alexei Olovnikov first recognized that chromosomes could not completely replicate their ends; this is known as the "end replication problem". Building on this, and accommodating Leonard Hayflick's idea of limited somatic cell division, Olovnikov suggested that DNA sequences are lost every time a cell replicates until the loss reaches a critical level, at which point cell division e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Replication
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a double helix of two complementary strands. The double helix describes the appearance of a double-stranded DNA which is thus composed of two linear strands that run opposite to each other and twist together to form. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result of semi-conservative re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts. Human mitochondrial DNA was the first significant part of the human genome to be sequenced. This sequencing revealed that the human mtDNA includes 16,569 base pairs and encodes 13 proteins. Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It also permits an examination of the relatedness of populations, and so has become important in anthropology and biogeography. Origin Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genes (journal)
''Genes'' is a quarterly peer-reviewed open access scientific journal that is published by MDPI. The editor-in-chief is J. Peter W. Young ( University of York). It covers all topics related to genes, genetics, and genomics. Abstracting and indexing The journal is abstracted and indexed in: * Chemical Abstracts * EBSCOhost * EMBASE * Science Citation Index Expanded * Scopus Scopus is Elsevier's abstract and citation database launched in 2004. Scopus covers nearly 36,377 titles (22,794 active titles and 13,583 inactive titles) from approximately 11,678 publishers, of which 34,346 are peer-reviewed journals in top-l ... References External links * {{Official website, http://www.mdpi.com/journal/genes/ Genetics journals Open access journals Publications established in 2010 Quarterly journals English-language journals MDPI academic journals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POT1
Protection of telomeres protein 1 is a protein that in humans is encoded by the ''POT1'' gene. Function This gene is a member of the telombin family and encodes a nuclear protein involved in telomere maintenance. Specifically, this protein functions as a member of a multi-protein complex known as shelterin, that binds to the TTAGGG repeats of telomeres, regulating telomere length and protecting chromosome ends from illegitimate recombination, catastrophic chromosome instability, and abnormal chromosome segregation. Alternatively spliced transcript variants have been described. The absence of POT1 in mouse embryonic fibroblasts and chicken cells leads to a detrimental DNA damage response on telomeres resulting in telomere dysfunction-induced foci (TIFs). POT1 is required for telomere protection because it allows for telomere inhibition of DNA damage response factors. The protein also serves a role in the regulation of telomerase activity on telomeres. In vitro experiments utilizi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAD51
DNA repair protein RAD51 homolog 1 is a protein encoded by the gene ''RAD51''. The enzyme encoded by this gene is a member of the RAD51 protein family which assists in repair of DNA double strand breaks. RAD51 family members are homologous to the bacterial RecA, Archaeal RadA and yeast Rad51. The protein is highly conserved in most eukaryotes, from yeast to humans. Variants Two alternatively spliced transcript variants of this gene, which encode distinct proteins, have been reported. Transcript variants utilizing alternative polyA signals exist. Family In mammals, seven recA-like genes have been identified: Rad51, Rad51L1/B, Rad51L2/C, Rad51L3/D, XRCC2, XRCC3, and DMC1/Lim15. All of these proteins, with the exception of meiosis-specific DMC1, are essential for development in mammals. Rad51 is a member of thRecA-like NTPases Function In humans, RAD51 is a 339-amino acid protein that plays a major role in homologous recombination of DNA during double strand b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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