 The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA is the long-term storage of information and it is often compared to a set of blueprints, since DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Image File history File links Download high resolution version (799x2000, 915 KB) Summary An overview of the structure of DNA. Created by Michael Ströck (mstroeck) on February 8, 2006. ...
Image File history File links Download high resolution version (799x2000, 915 KB) Summary An overview of the structure of DNA. Created by Michael Ströck (mstroeck) on February 8, 2006. ...
Look up nucleic acid in Wiktionary, the free dictionary. ...
DNA, the molecular basis for inheritance. ...
Views of a Foetus in the Womb, Leonardo da Vinci, ca. ...
For other uses, see Life (disambiguation). ...
Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ...
A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...
Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions...
In science, a molecule is a group of atoms in a definite arrangement held together by chemical bonds. ...
For a non-technical introduction to the topic, see Introduction to Genetics. ...
Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate atoms joined by ester bonds. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes. A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ...
A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ...
A carboxylic acid ester. ...
Adenine Guanine Thymine Cytosine ...
A series of codons in part of a mRNA molecule. ...
Phenylalanine is one of the standard amino acids. ...
Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions...
A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ...
Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ...
A spliceosome is a complex of RNA and many protein subunits called snRNPs, that removes the non-coding introns from unprocessed mRNA. Spliceosomes are unique to eukaryotic mRNA as the mRNA of prokaryotes lack introns. ...
Within cells, DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...
This does not adequately cite its references or sources. ...
It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...
Kingdoms Animalia - Animals Fungi Plantae - Plants Protista Alternative phylogeny Unikonta Opisthokonta Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ...
For other uses, see Animal (disambiguation). ...
Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants...
Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ...
HeLa cells stained for DNA with the Blue Hoechst dye. ...
Prokaryotes (pro-KAR-ee-oht) (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos, pl. ...
Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...
It has been suggested that Cytoplast be merged into this article or section. ...
Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ...
Schematic representation of the assembly of the core histones into the nucleosome. ...
This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...
Physical and chemical properties
 The chemical structure of DNA. DNA is a long polymer made from repeating units called nucleotides.[1][2] The DNA chain is 22 to 24 Ångströms wide (2.2 to 2.4 nanometres), and one nucleotide unit is 3.3 Ångstroms (0.33 nanometres) long.[3] Although each individual repeating unit is very small, DNA polymers can be enormous molecules containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is 220 million base pairs long.[4] Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ...
A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ...
An ångström or aangstroem (the official transliteration), or angstrom (symbol Å) is a non-SI unit of length that is internationally recognized, equal to 0. ...
A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ...
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
Base pairs, of a DNA molecule. ...
In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules.[5][6] These two long strands entwine like vines, in the shape of a double helix. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. If multiple nucleotides are linked together, as in DNA, this polymer is referred to as a polynucleotide.[7] A helix (pl: helices), from the Greek word Îλικας/Îλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ...
Nucleosides are glycosylamines made by attaching a nucleobase (often reffered to simply as bases) to a ribose ring. ...
A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ...
Polynucleotide literally means many nucleotides. ...
The backbone of the DNA strand is made from alternating phosphate and sugar residues.[8] The sugar in DNA is 2-deoxyribose, which is a pentose (five carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These asymmetric bonds mean a strand of DNA has a direction. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand. This arrangement of DNA strands is called antiparallel. The asymmetric ends of DNA strands are referred to as the 5′ (five prime) and 3′ (three prime) ends. One of the major differences between DNA and RNA is the sugar, with 2-deoxyribose being replaced by the alternative pentose sugar ribose in RNA.[6] Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ...
Lactose is a disaccharide found in milk. ...
A pentose is a monosaccharide with five carbon atoms. ...
General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ...
Diagram of phosphodiester bonds between nucleotides A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a phosphate group and two other molecules over two ester bonds. ...
Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle still characterizing a chemical element. ...
Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or sometimes between atoms and other covalent bonds. ...
A diagram of a furanose (sugar-ring) molecule with carbons labelled numerically Directionality, in molecular biology, refers to the end-to-end chemical orientation of a single strand of nucleic acid. ...
A diagram of a furanose (sugar-ring) molecule with carbons labelled numerically Directionality, in molecular biology, refers to the end-to-end chemical orientation of a single strand of nucleic acid. ...
Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ...
The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). These four bases are shown below and are attached to the sugar/phosphate to form the complete nucleotide, as shown for adenosine monophosphate. An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...
This article or section does not adequately cite its references or sources. ...
Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at...
Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. ...
For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...
These bases are classified into two types; adenine and guanine are fused five- and six-membered heterocyclic compounds called purines, while cytosine and thymine are six-membered rings called pyrimidines.[7] A fifth pyrimidine base, called uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine, but a very rare exception to this rule is a bacterial virus called PBS1 that contains uracil in its DNA.[9] In contrast, following synthesis of certain RNA molecules, a significant number of the uracils are converted to thymines by the enzymatic addition of the missing methyl group. This occurs mostly on structural and enzymatic RNAs like transfer RNAs and ribosomal RNA.[10] Pyridine a simple heterocyclic compound Heterocyclic compounds are organic compounds which contain a ring structure containing atoms in addition to carbon, such as sulfur, oxygen or nitrogen, as part of the ring. ...
Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ...
Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine. ...
Uracil is a pyrimidine which is common and naturally occurring. ...
In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ...
This article or section does not cite its references or sources. ...
It has been suggested that Queuine be merged into this article or section. ...
Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. ...
 Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands.
Large version[11] The double helix is a right-handed spiral. As the DNA strands wind around each other, they leave gaps between each set of phosphate backbones, revealing the sides of the bases inside (see animation). There are two of these grooves twisting around the surface of the double helix: one groove, the major groove, is 22 Å wide and the other, the minor groove, is 12 Å wide.[12] The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like transcription factors that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove.[13] Image File history File links DNA_orbit_animated_small. ...
Image File history File links No higher resolution available. ...
In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ...
Base pairing - Further information: Base pair
At top, a GC base pair with three hydrogen bonds. At the bottom, AT base pair with two hydrogen bonds. Hydrogen bonds are shown as dashed lines. Each type of base on one strand forms a bond with just one type of base on the other strand. This is called complementary base pairing. Here, purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G. This arrangement of two nucleotides binding together across the double helix is called a base pair. In a double helix, the two strands are also held together via forces generated by the hydrophobic effect and pi stacking, which are not influenced by the sequence of the DNA.[14] As hydrogen bonds are not covalent, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can therefore be pulled apart like a zipper, either by a mechanical force or high temperature.[15] As a result of this complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. Indeed, this reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms.[1] Base pairs, of a DNA molecule. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...
Base pairs, of a DNA molecule. ...
An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...
In physics, force is an influence that may cause an object to accelerate. ...
The hydrophobic effect is the property that nonpolar molecules like to self-associate in the presence of aqueous solution. ...
It has been suggested that this article or section be merged into Stacking (chemistry). ...
Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or sometimes between atoms and other covalent bonds. ...
This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ...
The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, left). The GC base pair is therefore stronger than the AT base pair. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determine the strength of the association between the two strands of DNA. Long DNA helices with a high GC content have stronger-interacting strands, while short helices with high AT content have weaker-interacting strands.[16] Parts of the DNA double helix that need to separate easily, such as the TATAAT Pribnow box in bacterial promoters, tend to have sequences with a high AT content, making the strands easier to pull apart.[17] In the laboratory, the strength of this interaction can be measured by finding the temperature required to break the hydrogen bonds, their melting temperature (also called Tm value). When all the base pairs in a DNA double helix melt, the strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others.[18] The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc. ...
A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ...
The dissociation of a double-stranded DNA molecule is often referred to as melting because it occurs quickly once a certain temperature has been reached. ...
Sense and antisense - Further information: Sense (molecular biology)
A DNA sequence is called "sense" if its sequence is the same as that of a messenger RNA copy that is translated into protein. The sequence on the opposite strand is complementary to the sense sequence and is therefore called the "antisense" sequence. Since RNA polymerases work by making a complementary copy of their templates, it is this antisense strand that is the template for producing the sense messenger RNA. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear.[19] One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing.[20] Sense, when applied in a molecular biology context, is a general concept used to compare the polarity of nucleic acid molecules, particularly RNA, to other nucleic acid molecules. ...
The life cycle of an mRNA in a eukaryotic cell. ...
This article does not cite any references or sources. ...
Gene expression, or simply expression, is the process by which a genes DNA sequence is converted into functional proteins. ...
A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses, blur the distinction made above between sense and antisense strands by having overlapping genes.[21] In these cases, some DNA sequences do double duty, encoding one protein when read 5′ to 3′ along one strand, and a second protein when read in the opposite direction (still 5′ to 3′) along the other strand. In bacteria, this overlap may be involved in the regulation of gene transcription,[22] while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome.[23] Another way of reducing genome size is seen in some viruses that contain linear or circular single-stranded DNA as their genetic material.[24][25] Figure 1: Schematic drawing of a bacterium with plasmids enclosed. ...
Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (from the Latin noun virus, meaning toxin or poison) is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the...
Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ...
Supercoiling - Further information: DNA supercoil
DNA can be twisted like a rope in a process called DNA supercoiling. With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound.[26] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that is introduced by enzymes called topoisomerases.[27] These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as transcription and DNA replication.[28] In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ...
In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ...
Topoisomerase I solves the problem caused by tension generated by winding/unwinding of DNA. It wraps around DNA and makes a cut permitting the helix to spin. ...
A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ...
It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...
 From left to right, the structures of A, B and Z DNA Image File history File links Download high-resolution version (2486x1620, 2113 KB) By Richard Wheeler (Zephyris) 2007. ...
Image File history File links Download high-resolution version (2486x1620, 2113 KB) By Richard Wheeler (Zephyris) 2007. ...
Alternative double-helical structures - Further information: Mechanical properties of DNA
DNA exists in several possible conformations. The conformations so far identified are: A-DNA, B-DNA, C-DNA, D-DNA,[29] E-DNA,[30] H-DNA,[31] L-DNA,[29] P-DNA,[32] and Z-DNA.[8][33] However, only A-DNA, B-DNA, and Z-DNA have been observed in naturally occurring biological systems. Which conformation DNA adopts depends on the sequence of the DNA, the amount and direction of supercoiling, chemical modifications of the bases and also solution conditions, such as the concentration of metal ions and polyamines.[34] Of these three conformations, the "B" form described above is most common under the conditions found in cells.[35] The two alternative double-helical forms of DNA differ in their geometry and dimensions. The mechanical properties of DNA are closly related to its molecular structure and the relative weakness of the hydrogen bonds and electronic interactions that hold strands of DNA together compared to the strength of the bonds within each strand. ...
Conformational isomerism is the phenomenon of molecules with the same structural formula but different conformations (conformers) of atoms about a rotating bond. ...
The A-DNA structure. ...
The Z-DNA structure. ...
Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ...
An electrostatic potential map of the nitrate ion (NO3−). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ...
The polyamines are organic compounds having two or more primary amino groups - such as putrescine, cadaverine, spermidine, and spermine - that are growth factors in both eucaryotic and procaryotic cells. ...
The A form is a wider right-handed spiral, with a shallow and wide minor groove and a narrower and deeper major groove. The A form occurs under non-physiological conditions in dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, as well as in enzyme-DNA complexes.[36][37] Segments of DNA where the bases have been chemically-modified by methylation may undergo a larger change in conformation and adopt the Z form. Here, the strands turn about the helical axis in a left-handed spiral, the opposite of the more common B form.[38] These unusual structures can be recognised by specific Z-DNA binding proteins and may be involved in the regulation of transcription.[39] Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ...
The Z-DNA structure. ...
 Structure of a DNA quadruplex formed by telomere repeats. The conformation of the DNA backbone diverges significantly from the typical helical structure [40] Image File history File links Size of this preview: 658 × 600 pixelsFull resolution (1316 × 1200 pixel, file size: 1. ...
Image File history File links Size of this preview: 658 × 600 pixelsFull resolution (1316 × 1200 pixel, file size: 1. ...
A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...
Quadruplex structures At the ends of the linear chromosomes are specialized regions of DNA called telomeres. The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme telomerase, as the enzymes that normally replicate DNA cannot copy the extreme 3′ ends of chromosomes.[41] As a result, if a chromosome lacked telomeres it would become shorter each time it was replicated. These specialized chromosome caps also help protect the DNA ends from exonucleases and stop the DNA repair systems in the cell from treating them as damage to be corrected.[42] In human cells, telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence.[43] Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...
Telomerase is an enzyme that adds specific DNA sequence repeats (TTAGGG in all vertebrates) to the 3 (three prime) end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. ...
Exonucleases are enzymes that cleave nucleotides one at a time from an end of a polynucleotide chain. ...
DNA damage resulting in multiple broken chromosomes DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. ...
These guanine-rich sequences may stabilize chromosome ends by forming very unusual structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases form a flat plate and these flat four-base units then stack on top of each other, to form a stable G-quadruplex structure.[44] These structures are stabilized by hydrogen bonding between the edges of the bases and chelation of a metal ion in the centre of each four-base unit. The structure shown to the left is a top view of the quadruplex formed by a DNA sequence found in human telomere repeats. The single DNA strand forms a loop, with the sets of four bases stacking in a central quadruplex three plates deep. In the space at the centre of the stacked bases are three chelated potassium ions.[45] Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. Nucleic acid sequences which are rich in guanine are capable of forming four-stranded structures called G-quadruplexes (Also known as G-tetrads or G4-DNA). ...
Chelation (from Greek χηλή, chelè, meaning claw) is the process of reversible binding (complexation) of a ligand - the chelant, chelator, chelating agent, sequestering agent, or complexing agent - to a metal ion, forming a metal complex, the chelate. ...
General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Standard atomic weight 39. ...
In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here, the single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins.[46] At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This triple-stranded structure is called a displacement loop or D-loop.[44]
Chemical modifications Structure of cytosine with and without the 5-methyl group. After deamination the 5-methylcytosine has the same structure as thymine Download high resolution version (1014x1357, 5 KB) Wikipedia does not have an article with this exact name. ...
Image File history File links Size of this preview: 582 × 599 pixelsFull resolution (1202 × 1238 pixel, file size: 5 KB, MIME type: image/png) Chemical structure of 5-methylcytosine. ...
Download high resolution version (1269x1363, 6 KB) Wikipedia does not have an article with this exact name. ...
Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at...
5-methylcytosine is the methylated form of cytosine. ...
For the similarly-spelled vitamin compound, see Thiamine Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ...
Base modifications - Further information: DNA methylation
The expression of genes is influenced by the chromatin structure of a chromosome and regions of heterochromatin (low or no gene expression) correlate with the methylation of cytosine. For example, cytosine methylation, to produce 5-methylcytosine, is important for X-chromosome inactivation.[47] The average level of methylation varies between organisms, with Caenorhabditis elegans lacking cytosine methylation, while vertebrates show higher levels, with up to 1% of their DNA containing 5-methylcytosine.[48] Despite the biological role of 5-methylcytosine it is susceptible to spontaneous deamination to leave the thymine base, and methylated cytosines are therefore mutation hotspots.[49] Other base modifications include adenine methylation in bacteria and the glycosylation of uracil to produce the "J-base" in kinetoplastids.[50][51] DNA methylation is a type of chemical modification of DNA that can be inherited without changing the DNA sequence. ...
Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ...
For differently-colored eyes, see Heterochromia. ...
Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ...
Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at...
5-methylcytosine is the methylated form of cytosine. ...
In those species in which sex is determined by the presence of the Y or W chromosome rather than the diploidy of the X or Z, a Barr body is the inactive X chromosome in a female cell, or the inactive Z in a male. ...
Binomial name Caenorhabditis elegans Maupas, 1900 Caenorhabditis elegans (IPA: ) is a free-living nematode (roundworm), about 1 mm in length, which lives in temperate soil environments. ...
This article does not cite any references or sources. ...
Deamination is the removal of an amine group from a molecule. ...
It has been suggested that mutant be merged into this article or section. ...
Glycosylation is the process or result of addition of saccharides to proteins and lipids. ...
Orders Trypanosomatida Bodonida The kinetoplastids are a group of flagellate protozoa, including a number of parasites responsible for serious diseases in humans and other animals, as well as various forms found in soil and aquatic environments. ...
DNA damage - Further information: Mutation
DNA can be damaged by many different sorts of mutagens. These include oxidizing agents, alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and x-rays. The type of DNA damage produced depends on the type of mutagen. For example, UV light mostly damages DNA by producing thymine dimers, which are cross-links between adjacent pyrimidine bases in a DNA strand.[53] On the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, as well as double-strand breaks.[54] It has been estimated that in each human cell, about 500 bases suffer oxidative damage per day.[55][56] Of these oxidative lesions, the most dangerous are double-strand breaks, as these lesions are difficult to repair and can produce point mutations, insertions and deletions from the DNA sequence, as well as chromosomal translocations.[57] It has been suggested that mutant be merged into this article or section. ...
Image File history File links Download high-resolution version (1131x1566, 915 KB)By Richard Wheeler (Zephyris) 2007. ...
Image File history File links Download high-resolution version (1131x1566, 915 KB)By Richard Wheeler (Zephyris) 2007. ...
Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. ...
The cigarette is the most common method of smoking tobacco. ...
In biology, a mutagen (Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ...
European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ...
Alkylating agents are so named because of their ability to add alkyl groups to many electronegative groups under conditions present in cells. ...
Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ...
“UV†redirects here. ...
In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...
A thymine dimer happens when two adjacent thymine residues in a DNA molecule, get chemically bonded to each other. ...
In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...
Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ...
A point mutation, or substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide. ...
An illustration of an insertion at chromosome level At DNA level, an insertion means the insertion of a few base pairs into a genetic sequence. ...
A genetic deletion is a genetic aberration in which part of a chromosome is missing. ...
Chromosomal translocation of the 4th and 20th chromosome. ...
Many mutagens intercalate into the space between two adjacent base pairs. Intercalators are mostly aromatic and planar molecules, and include ethidium, daunomycin, doxorubicin and thalidomide. In order for an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. These structural changes inhibit both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators are often carcinogens, with benzopyrene diol epoxide, acridines, aflatoxin and ethidium bromide being well-known examples.[58][59][60] Nevertheless, due to their properties of inhibiting DNA transcription and replication, they are also used in chemotherapy to inhibit rapidly-growing cancer cells.[61] Intercalation induces structural distortions. ...
Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ...
Ethidium bromide - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ...
Daunorubicin or daunomycin (daunomycin cerubidine) is chemotherapy of the anthracycline family that is given as a treatment for some types of cancer. ...
Doxorubicin or Adriamycin® or hydroxyldaunorubicin is a DNA-interacting drug widely used in chemotherapy. ...
// Thalidomide is a sedative, hypnotic, and anti-inflammatory medication. ...
The hazard symbol for carcinogenic chemicals in the Globally Harmonized System. ...
Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. ...
Acridine, C13H9N, is an organic compound and a nitrogen heterocycle. ...
Chemical structure of aflatoxin B1 Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, most notably Aspergillus flavus and Aspergillus parasiticus. ...
R-phrases , S-phrases , , , , , Flash point > 100 °C Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references Absorption spectrum of ethidium bromide Ethidium bromide (sometimes abbreviated as EtBr) is an intercalating agent commonly used as a nucleic...
Chemotherapy is the use of chemical substances to treat disease. ...
Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...
Overview of biological functions DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes.[62] The information carried by DNA is held in the sequence of pieces of DNA called genes. Transmission of genetic information in genes is achieved via complementary base pairing. For example, in transcription, when a cell uses the information in a gene, the DNA sequence is copied into a complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides. Usually, this RNA copy is then used to make a matching protein sequence in a process called translation which depends on the same interaction between RNA nucleotides. Alternatively, a cell may simply copy its genetic information in a process called DNA replication. The details of these functions are covered in other articles; here we focus on the interactions between DNA and other molecules that mediate the function of the genome. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...
A graphical representation of the normal human karyotype. ...
part of a DNA sequence A DNA sequence (sometimes genetic sequence) is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, The possible letters are A, C, G, and T, representing the four nucleotide subunits of a DNA strand (adenine, cytosine, guanine...
For a non-technical introduction to the topic, see Introduction to Genetics. ...
Genetic transmission is the transfer of genetic information from genes to another generation, or from one location in a cell to another. ...
Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...
Genome structure - Further information: Cell nucleus, Chromatin, Chromosome, Gene, Non-coding DNA
Genomic DNA is located in the cell nucleus of eukaryotes, as well as small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid.[63] The genetic information in a genome is held within genes. A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism. Genes contain an open reading frame that can be transcribed, as well as regulatory sequences such as promoters and enhancers, which control the expression of the open reading frame. HeLa cells stained for DNA with the Blue Hoechst dye. ...
Chromatin is the complex of DNA and protein found inside the nuclei of eukaryotic cells. ...
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
For a non-technical introduction to the topic, see Introduction to Genetics. ...
In genetics, noncoding DNA describes DNA which does not contain instructions for making proteins (or other cell products such as RNAs). ...
HeLa cells stained for DNA with the Blue Hoechst dye. ...
Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) (from Greek μιτος or mitos, thread + χονδÏιον or khondrion, granule) is a membrane-enclosed organelle, found in most eukaryotic cells. ...
Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ...
It has been suggested that Genophore be merged into this article or section. ...
Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring through their genes, or the transfer of a title, style or social status through the social convention known as inheritance (for example, a Hereditary Title may be passed down according to relevant customs and/or laws). ...
An open reading frame or ORF is any sequence of DNA or RNA that can be translated into a protein. ...
A regulatory sequence (also called regulatory region or ~ element) is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ...
A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ...
In genetics, an enhancer is a short region of DNA that can be bound with proteins (namely, the trans-acting factors, much like a set of transcription factors) to enhance transcription levels of genes (hence the name) in a gene-cluster. ...
In many species, only a small fraction of the total sequence of the genome encodes protein. For example, only about 1.5% of the human genome consists of protein-coding exons, with over 50% of human DNA consisting of non-coding repetitive sequences.[64] The reasons for the presence of so much non-coding DNA in eukaryotic genomes and the extraordinary differences in genome size, or C-value, among species represent a long-standing puzzle known as the "C-value enigma."[65] However, DNA sequences that do not code protein may still encode functional non-coding RNA molecules, which are involved in the regulation of gene expression.[66] In biology, a species is one of the basic units of biodiversity. ...
In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...
An exon is any region of DNA within a gene, that is transcribed to the final messenger RNA (mRNA) molecule, rather than being spliced out from the transcribed RNA molecule. ...
In the study of DNA sequences, one can distinguish two main types of repeated sequence: Tandem repeats: Satellite DNA, Minisatellite, Microsatellite; Interspersed repeats: SINEs (Short INterspersed Elements), LINEs (Long INterspersed Elements). ...
It has been suggested that junk DNA be merged into this article or section. ...
Genome size refers to the total amount of DNA contained within one copy of a genome. ...
The term C-value refers to the amount of DNA contained within a haploid nucleus (e. ...
// Definition and origin The C-value enigma is a term used to describe the complex puzzle surrounding the extensive variation in nuclear genome size among eukaryotic species. ...
A non-coding RNA (ncRNA) is any RNA molecule that is not translated into a protein. ...
Some non-coding DNA sequences play structural roles in chromosomes. Telomeres and centromeres typically contain few genes, but are important for the function and stability of chromosomes.[42][68] An abundant form of non-coding DNA in humans are pseudogenes, which are copies of genes that have been disabled by mutation.[69] These sequences are usually just molecular fossils, although they can occasionally serve as raw genetic material for the creation of new genes through the process of gene duplication and divergence.[70] Image File history File links Size of this preview: 800 × 554 pixelsFull resolution (1348 × 934 pixel, file size: 791 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Image File history File links Size of this preview: 800 × 554 pixelsFull resolution (1348 × 934 pixel, file size: 791 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
T7 RNA Polymerase is an RNA polymerase that catalyzes the formation of RNA in the 5→ 3 direction. ...
A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...
The centromere is a region of chromosomes with a special sequence and structure. ...
A pseudogene is a nucleotide sequences that is similar to a normal gene, but is not expressed as a functional protein. ...
FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL is an acronym for Fido Opus Seadog Standard Interface Layer. ...
Schematic of a region of a chromosome before and after a duplication event Gene duplication occurs when an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome leads to the duplication of a region of DNA containing a gene [1]. The significance of this process for...
Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time. ...
Transcription and translation - Further information: Genetic code, Transcription (genetics), Protein biosynthesis
A gene is a sequence of DNA that contains genetic information and can influence the phenotype of an organism. Within a gene, the sequence of bases along a DNA strand defines a messenger RNA sequence, which then defines a protein sequence. The relationship between the nucleotide sequences of genes and the amino-acid sequences of proteins is determined by the rules of translation, known collectively as the genetic code. The genetic code consists of three-letter 'words' called codons formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). A series of codons in part of a mRNA molecule. ...
A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ...
An overview of protein synthesis. ...
Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ...
The life cycle of an mRNA in a eukaryotic cell. ...
Phenylalanine is one of the standard amino acids. ...
Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...
A series of codons in part of a mRNA molecule. ...
In transcription, the codons of a gene are copied into messenger RNA by RNA polymerase. This RNA copy is then decoded by a ribosome that reads the RNA sequence by base-pairing the messenger RNA to transfer RNA, which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (43 combinations). These encode the twenty standard amino acids, giving most amino acids more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region; these are the TAA, TGA and TAG codons. This article does not cite any references or sources. ...
Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ...
It has been suggested that Queuine be merged into this article or section. ...
This list of standard proteinogenic amino acids details the chemical structures and properties of the twenty standard amino acids used in proteins by living cells. ...
 DNA replication. The double helix is unwound by a |
