DNA - Knowledge

3822: 3593:(SELEX). DNAzymes catalyze variety of chemical reactions including RNA-DNA cleavage, RNA-DNA ligation, amino acids phosphorylation-dephosphorylation, carbon-carbon bond formation, etc. DNAzymes can enhance catalytic rate of chemical reactions up to 100,000,000,000-fold over the uncatalyzed reaction. The most extensively studied class of DNAzymes is RNA-cleaving types which have been used to detect different metal ions and designing therapeutic agents. Several metal-specific DNAzymes have been reported including the GR-5 DNAzyme (lead-specific), the CA1-3 DNAzymes (copper-specific), the 39E DNAzyme (uranyl-specific) and the NaA43 DNAzyme (sodium-specific). The NaA43 DNAzyme, which is reported to be more than 10,000-fold selective for sodium over other metal ions, was used to make a real-time sodium sensor in cells. 3281:, in which a segment of a single strand in each helix is annealed to the complementary strand in the other helix. The Holliday junction is a tetrahedral junction structure that can be moved along the pair of chromosomes, swapping one strand for another. The recombination reaction is then halted by cleavage of the junction and re-ligation of the released DNA. Only strands of like polarity exchange DNA during recombination. There are two types of cleavage: east-west cleavage and north–south cleavage. The north–south cleavage nicks both strands of DNA, while the east–west cleavage has one strand of DNA intact. The formation of a Holliday junction during recombination makes it possible for genetic diversity, genes to exchange on chromosomes, and expression of wild-type viral genomes. 4089: 43: 592: 1507: 176: 124: 3975: 2907:, which are proteins that regulate transcription. Each transcription factor binds to one particular set of DNA sequences and activates or inhibits the transcription of genes that have these sequences close to their promoters. The transcription factors do this in two ways. Firstly, they can bind the RNA polymerase responsible for transcription, either directly or through other mediator proteins; this locates the polymerase at the promoter and allows it to begin transcription. Alternatively, transcription factors can bind 1656:. 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. 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 343: 2052: 2229: 1855: 3196: 102: 880: 15668: 2892: 1295: 15580: 14752: 457: 1942: 2691: 3187: 1935: 152: 3682: 2746:. This enzyme makes the complementary strand by finding the correct base through complementary base pairing and bonding it onto the original strand. As DNA polymerases can only extend a DNA strand in a 5′ to 3′ direction, different mechanisms are used to copy the antiparallel strands of the double helix. In this way, the base on the old strand dictates which base appears on the new strand, and the cell ends up with a perfect copy of its DNA. 2386: 2095: 2569: 15606: 4109:, in which they said, "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material." This letter was followed by a letter from Franklin and Gosling, which was the first publication of their own X-ray diffraction data and of their original analysis method. Then followed a letter by Wilkins and two of his colleagues, which contained an analysis of 15651: 1695: 14225: 15685: 2324:, due to normal cellular processes that produce reactive oxygen species, the hydrolytic activities of cellular water, etc., also occur frequently. Although most of these damages are repaired, in any cell some DNA damage may remain despite the action of repair processes. These remaining DNA damages accumulate with age in mammalian postmitotic tissues. This accumulation appears to be an important underlying cause of aging. 1356: 1343: 3320:

there is no direct evidence of ancient genetic systems, as recovery of DNA from most fossils is impossible because DNA survives in the environment for less than one million years, and slowly degrades into short fragments in solution. Claims for older DNA have been made, most notably a report of the isolation of a viable bacterium from a salt crystal 250 million years old, but these claims are controversial.

15634: 2827: 2938: 2088: 1310:. As the strands are not symmetrically located with respect to each other, the grooves are unequally sized. The major groove is 22 ångströms (2.2 nm) wide, while the minor groove is 12 Å (1.2 nm) in width. Due to the larger width of the major groove, the edges of the bases are more accessible in the major groove than in the minor groove. As a result, proteins such as 2102: 1998:. Dubbed S, B, P, and Z, these artificial bases are capable of bonding with each other in a predictable way (S–B and P–Z), maintain the double helix structure of DNA, and be transcribed to RNA. Their existence could be seen as an indication that there is nothing special about the four natural nucleobases that evolved on Earth. On the other hand, DNA is tightly related to 3219: 1418:. As a result of this base pair complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in organisms. 3223:

recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above. NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above. Most recombination events appear to be the SDSA type.

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and was critical to their obtaining the correct structure of DNA. Franklin told Crick and Watson that the backbones had to be on the outside. Before then, Linus Pauling, and Watson and Crick, had erroneous models with the chains inside and the bases pointing outwards. Franklin's identification of the

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properties of DNA and other nucleic acids to create self-assembling branched DNA complexes with useful properties. DNA is thus used as a structural material rather than as a carrier of biological information. This has led to the creation of two-dimensional periodic lattices (both tile-based and using

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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

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to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across the double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with

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On p. 264, Kossel remarked presciently: Der Erforschung der quantitativen Verhältnisse der vier stickstoffreichen Basen, der Abhängigkeit ihrer Menge von den physiologischen Zuständen der Zelle, verspricht wichtige Aufschlüsse über die elementaren physiologisch-chemischen Vorgänge. (The study of the

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law in some places, this can allow cases to be reopened where prior trials have failed to produce sufficient evidence to convince a jury. People charged with serious crimes may be required to provide a sample of DNA for matching purposes. The most obvious defense to DNA matches obtained forensically

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The development of forensic science and the ability to now obtain genetic matching on minute samples of blood, skin, saliva, or hair has led to re-examining many cases. Evidence can now be uncovered that was scientifically impossible at the time of the original examination. Combined with the removal

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Therefore, any DNA strand normally has one end at which there is a phosphate group attached to the 5′ carbon of a ribose (the 5′ phosphoryl) and another end at which there is a free hydroxyl group attached to the 3′ carbon of a ribose (the 3′ hydroxyl). The orientation of the 3′ and 5′ carbons along

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of the current genetic code based on four nucleotide bases. This would occur, since the number of different bases in such an organism is a trade-off between a small number of bases increasing replication accuracy and a large number of bases increasing the catalytic efficiency of ribozymes. However,

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Naked extracellular DNA (eDNA), most of it released by cell death, is nearly ubiquitous in the environment. Its concentration in soil may be as high as 2 μg/L, and its concentration in natural aquatic environments may be as high at 88 μg/L. Various possible functions have been proposed for eDNA: it

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produce multiple forms of damage, including base modifications, particularly of guanosine, and double-strand breaks. A typical human cell contains about 150,000 bases that have suffered oxidative damage. Of these oxidative lesions, the most dangerous are double-strand breaks, as these are difficult

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spiral, with a shallow, wide minor groove and a narrower, deeper major groove. The A form occurs under non-physiological conditions in partly dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, and in enzyme-DNA complexes. Segments of DNA where

923:). The pair of chains have a radius of 10 Å (1.0 nm). According to another study, when measured in a different solution, the DNA chain measured 22–26 Å (2.2–2.6 nm) wide, and one nucleotide unit measured 3.3 Å (0.33 nm) long. The buoyant density of most DNA is 1.7g/cm. 8081:

A certain irreducible background incidence of cancer is to be expected regardless of circumstances: mutations can never be absolutely avoided, because they are an inescapable consequence of fundamental limitations on the accuracy of DNA replication, as discussed in Chapter 5. If a human could live

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A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with an homologous chromosome and strand invasion to initiate the recombinational repair process. Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions. CO

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occurs when non-complementary regions exist at the end of an otherwise complementary double-strand of DNA. However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the

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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. At the very end of the T-loop, the single-stranded telomere DNA is held onto a

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necessary to break half of the hydrogen bonds. 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.

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in DNA. Some of these enzymes work by cutting the DNA helix and allowing one section to rotate, thereby reducing its level of supercoiling; the enzyme then seals the DNA break. Other types of these enzymes are capable of cutting one DNA helix and then passing a second strand of DNA through this

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identified the base, sugar, and phosphate nucleotide unit of RNA (then named "yeast nucleic acid"). In 1929, Levene identified deoxyribose sugar in "thymus nucleic acid" (DNA). Levene suggested that DNA consisted of a string of four nucleotide units linked together through the phosphate groups

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and development. The specificity of these transcription factors' interactions with DNA come from the proteins making multiple contacts to the edges of the DNA bases, allowing them to "read" the DNA sequence. Most of these base-interactions are made in the major groove, where the bases are most

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and changing the rate of transcription. Other non-specific DNA-binding proteins in chromatin include the high-mobility group proteins, which bind to bent or distorted DNA. These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up

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of the University of Leicester to verify or disprove a suspect's rape-murder "confession". In this particular case, the suspect had confessed to two rape-murders, but had later retracted his confession. DNA testing at the university labs soon disproved the veracity of the suspect's original

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copy that is translated into protein. The sequence on the opposite strand is called the "antisense" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands can contain both sense and antisense sequences). In both prokaryotes and

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is most common under the conditions found in cells, it is not a well-defined conformation but a family of related DNA conformations that occur at the high hydration levels present in cells. Their corresponding X-ray diffraction and scattering patterns are characteristic of molecular

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forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. The conformation that DNA adopts depends on the hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal

3536:, are compared between people. This method is usually an extremely reliable technique for identifying a matching DNA. However, identification can be complicated if the scene is contaminated with DNA from several people. DNA profiling was developed in 1984 by British geneticist Sir 2763:

of several bacterial species. It may act as a recognition factor to regulate the attachment and dispersal of specific cell types in the biofilm; it may contribute to biofilm formation; and it may contribute to the biofilm's physical strength and resistance to biological stress.

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which does not only act as a transcript of DNA but also performs as molecular machines many tasks in cells. For this purpose it has to fold into a structure. It has been shown that to allow to create all possible structures at least four bases are required for the corresponding

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of a metal ion in the centre of each four-base unit. 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.

12384:(Therefore, in my experiments I subsequently limited myself to the whole nucleus, leaving to a more favorable material the separation of the substances, that for the present, without further prejudice, I will designate as soluble and insoluble nuclear material ("Nuclein")) 3666:

and their possible functions in an organism even before they have been isolated experimentally. Entire genomes may also be compared, which can shed light on the evolutionary history of particular organism and permit the examination of complex evolutionary events.

12827:. By this term I designate the axial thread of the chromosome, in which the geneticists locate the linear combination of genes; … In the normal chromosome there is usually only one genoneme; before cell-division this genoneme has become divided into two strands." 2353:. For an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. This inhibits both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators may be 1583:

forms closed circular molecules, each of which contains 16,569 DNA base pairs, with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules. Each human

3658:, are difficult to use without the annotations that identify the locations of genes and regulatory elements on each chromosome. Regions of DNA sequence that have the characteristic patterns associated with protein- or RNA-coding genes can be identified by 13521:"What Rosalind Franklin truly contributed to the discovery of DNA's structure – Franklin was no victim in how the DNA double helix was solved. An overlooked letter and an unpublished news article, both written in 1953, reveal that she was an equal player" 2729:

is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. The double-stranded structure of DNA provides a simple mechanism for

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is the best-understood member of this family and is used in processes where the double helix is separated, including DNA replication, recombination, and DNA repair. These binding proteins seem to stabilize single-stranded DNA and protect it from forming

3139:, which is required for the replication of telomeres. For example, HIV reverse transcriptase is an enzyme for AIDS virus replication. Telomerase is an unusual polymerase because it contains its own RNA template as part of its structure. It synthesizes 3091:

of these enzymes, the incoming nucleoside triphosphate base-pairs to the template: this allows polymerases to accurately synthesize the complementary strand of their template. Polymerases are classified according to the type of template that they use.

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present in bacteria. This enzyme system acts at least in part as a molecular immune system protecting bacteria from infection by viruses. Modifications of the bases cytosine and adenine, the more common and modified DNA bases, play vital roles in the

1013:. The asymmetric ends of DNA strands are said to have a directionality of five prime end (5′ ), and three prime end (3′), with the 5′ end having a terminal phosphate group and the 3′ end a terminal hydroxyl group. One major difference between DNA and 4120:

In April 2023, scientists, based on new evidence, concluded that Rosalind Franklin was a contributor and "equal player" in the discovery process of DNA, rather than otherwise, as may have been presented subsequently after the time of the discovery.

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proposed a model for nucleic acids containing three intertwined chains, with the phosphates near the axis, and the bases on the outside. Watson and Crick completed their model, which is now accepted as the first correct model of the double helix of

1803:. Here, the strands turn about the helical axis in a left-handed spiral, the opposite of the more common B form. These unusual structures can be recognized by specific Z-DNA binding proteins and may be involved in the regulation of transcription. 12029:

Andersen ES, Dong M, Nielsen MM, Jahn K, Subramani R, Mamdouh W, Golas MM, Sander B, Stark H, Oliveira CL, Pedersen JS, Birkedal V, Besenbacher F, Gothelf KV, Kjems J (May 2009). "Self-assembly of a nanoscale DNA box with a controllable lid".

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Most DNA molecules are actually two polymer strands, bound together in a helical fashion by noncovalent bonds; this double-stranded (dsDNA) structure is maintained largely by the intrastrand base stacking interactions, which are strongest for

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value), which is the temperature at which 50% of the double-strand molecules are converted to single-strand molecules; melting temperature is dependent on ionic strength and the concentration of DNA. As a result, it is both the percentage of

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Gommers-Ampt JH, Van Leeuwen F, de Beer AL, Vliegenthart JF, Dizdaroglu M, Kowalak JA, Crain PF, Borst P (December 1993). "beta-D-glucosyl-hydroxymethyluracil: a novel modified base present in the DNA of the parasitic protozoan T. brucei".

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Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called

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can be non-specific, or the protein can bind specifically to a single DNA sequence. Enzymes can also bind to DNA and of these, the polymerases that copy the DNA base sequence in transcription and DNA replication are particularly important.

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make copies of DNA polynucleotide chains. To preserve biological information, it is essential that the sequence of bases in each copy are precisely complementary to the sequence of bases in the template strand. Many DNA polymerases have a

4135:, which foretold the relationship between DNA, RNA, and proteins, and articulated the "adaptor hypothesis". Final confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 through the 1547:

per cell extends for 6.37 Gigabase pairs (Gbp), is 208.23 cm long and weighs 6.51 picograms (pg). Male values are 6.27 Gbp, 205.00 cm, 6.41 pg. Each DNA polymer can contain hundreds of millions of nucleotides, such as in

13488:"Untangling Rosalind Franklin's Role in DNA Discovery, 70 Years On – Historians have long debated the role that Dr. Franklin played in identifying the double helix. A new opinion essay argues that she was an "equal contributor."" 593: 12381:

Ich habe mich daher später mit meinen Versuchen an die ganzen Kerne gehalten, die Trennung der Körper, die ich einstweilen ohne weiteres Präjudiz als lösliches und unlösliches Nuclein bezeichnen will, einem günstigeren Material

2676:, 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 TAG, TAA, and TGA codons, (UAG, UAA, and UGA on the mRNA). 3634:. String searching or matching algorithms, which find an occurrence of a sequence of letters inside a larger sequence of letters, were developed to search for specific sequences of nucleotides. The DNA sequence may be 3556:

DNA profiling is also used successfully to positively identify victims of mass casualty incidents, bodies or body parts in serious accidents, and individual victims in mass war graves, via matching to family members.

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These guanine-rich sequences may stabilize chromosome ends by forming structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases, known as a

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that copies the sequence of a DNA strand into RNA. To begin transcribing a gene, the RNA polymerase binds to a sequence of DNA called a promoter and separates the DNA strands. It then copies the gene sequence into a

3917:. At the time, "yeast nucleic acid" (RNA) was thought to occur only in plants, while "thymus nucleic acid" (DNA) only in animals. The latter was thought to be a tetramer, with the function of buffering cellular pH. 12560:

quantitative relations of the four nitrogenous bases— of the dependence of their quantity on the physiological states of the cell—promises important insights into the fundamental physiological-chemical processes.)

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As these DNA targets can occur throughout an organism's genome, changes in the activity of one type of transcription factor can affect thousands of genes. Consequently, these proteins are often the targets of the

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could be transferred to the "rough" form of the same bacteria by mixing killed "smooth" bacteria with the live "rough" form. This system provided the first clear suggestion that DNA carries genetic information.

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proposed that inherited traits would be inherited via a "giant hereditary molecule" made up of "two mirror strands that would replicate in a semi-conservative fashion using each strand as a template". In 1928,

3585:, also called DNAzymes or catalytic DNA, were first discovered in 1994. They are mostly single stranded DNA sequences isolated from a large pool of random DNA sequences through a combinatorial approach called 7868:

Douki T, Reynaud-Angelin A, Cadet J, Sage E (August 2003). "Bipyrimidine photoproducts rather than oxidative lesions are the main type of DNA damage involved in the genotoxic effect of solar UVA radiation".

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that can bind to specific sequences in double-stranded DNA usually make contact with the sides of the bases exposed in the major groove. This situation varies in unusual conformations of DNA within the cell

2983:, which cut DNA at specific sequences. For instance, the EcoRV enzyme shown to the left recognizes the 6-base sequence 5′-GATATC-3′ and makes a cut at the horizontal line. In nature, these enzymes protect 3754:

Because DNA collects mutations over time, which are then inherited, it contains historical information, and, by comparing DNA sequences, geneticists can infer the evolutionary history of organisms, their

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to determine if someone is the biological parent or grandparent of a child with the probability of parentage is typically 99.99% when the alleged parent is biologically related to the child. Normal

13096:"Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III" 1588:

contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500. However, the amount of mitochondria per cell also varies by cell type, and an

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activity. Here, the polymerase recognizes the occasional mistakes in the synthesis reaction by the lack of base pairing between the mismatched nucleotides. If a mismatch is detected, a 3′ to 5′

1638:, this overlap may be involved in the regulation of gene transcription, while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome. 3231:". This physical separation of different chromosomes is important for the ability of DNA to function as a stable repository for information, as one of the few times chromosomes interact is in 1306:

Twin helical strands form the DNA backbone. Another double helix may be found tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a

3060:(ATP), to break hydrogen bonds between bases and unwind the DNA double helix into single strands. These enzymes are essential for most processes where enzymes need to access the DNA bases. 1448:

basepairs) but also on sequence (since stacking is sequence specific) and also length (longer molecules are more stable). The stability can be measured in various ways; a common way is the

907:. The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. In all species it is composed of two helical chains, bound to each other by 1634:. In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. In 6218:

Basu HS, Feuerstein BG, Zarling DA, Shafer RH, Marton LJ (October 1988). "Recognition of Z-RNA and Z-DNA determinants by polyamines in solution: experimental and theoretical studies".

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DNA has performed this function, as it has been proposed that the earliest forms of life may have used RNA as their genetic material. RNA may have acted as the central part of early

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has been recovered from ancient organisms at a timescale where genome evolution can be directly observed, including from extinct organisms up to millions of years old, such as the

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and can be important in the rapid evolution of new proteins. Genetic recombination can also be involved in DNA repair, particularly in the cell's response to double-strand breaks.

5531:"Single-stranded adenine-rich DNA and RNA retain structural characteristics of their respective double-stranded conformations and show directional differences in stacking pattern" 1840:

was announced, though the research was disputed, and evidence suggests the bacterium actively prevents the incorporation of arsenic into the DNA backbone and other biomolecules.

2851:, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones, making 1972:

simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible. Branched DNA can be used in

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DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. These two long strands coil around each other, in the shape of a

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deHaseth PL, Helmann JD (June 1995). "Open complex formation by Escherichia coli RNA polymerase: the mechanism of polymerase-induced strand separation of double helical DNA".

2759:; it may provide nutrients; and it may act as a buffer to recruit or titrate ions or antibiotics. Extracellular DNA acts as a functional extracellular matrix component in the 2446:. The details of these functions are covered in other articles; here the focus is on the interactions between DNA and other molecules that mediate the function of the genome. 14840: 11084:"Million-year-old mammoth genomes shatter record for oldest ancient DNA – Permafrost-preserved teeth, up to 1.6 million years old, identify a new kind of mammoth in Siberia" 2855:

to the acidic sugar-phosphate backbone of the DNA, and are thus largely independent of the base sequence. Chemical modifications of these basic amino acid residues include

1874:, as the enzymes that normally replicate DNA cannot copy the extreme 3′ ends of chromosomes. These specialized chromosome caps also help protect the DNA ends, and stop the 1433:

stacks. The two strands can come apart—a process known as melting—to form two single-stranded DNA (ssDNA) molecules. Melting occurs at high temperatures, low salt and high

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form DNA adducts that induce errors in replication. Nevertheless, due to their ability to inhibit DNA transcription and replication, other similar toxins are also used in

1742: 1414:, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can thus be pulled apart like a zipper, either by a mechanical force or high 11032: 1615:

eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear. One proposal is that antisense RNAs are involved in regulating

871:, compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed. 4872:"RCSB PDB – 1D65: Molecular structure of the B-DNA dodecamer d(CGCAAATTTGCG)2. An examination of propeller twist and minor-groove water structure at 2.2 A resolution" 4102:

published a series of five articles giving the Watson and Crick double-helix structure DNA and evidence supporting it. The structure was reported in a letter titled "

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base pairs and the overall length of a DNA double helix that determines the strength of the association between the two strands of DNA. Long DNA helices with a high

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of Earth that uses radically different biochemical and molecular processes than currently known life. One of the proposals was the existence of lifeforms that use

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A DNA helix usually does not interact with other segments of DNA, and in human cells, the different chromosomes even occupy separate areas in the nucleus called "

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Rothenburg S, Koch-Nolte F, Haag F (December 2001). "DNA methylation and Z-DNA formation as mediators of quantitative differences in the expression of alleles".

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Anderson S, Bankier AT, Barrell BG, de Bruijn MH, Coulson AR, Drouin J, et al. (April 1981). "Sequence and organization of the human mitochondrial genome".

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Goff SP, Berg P (December 1976). "Construction of hybrid viruses containing SV40 and lambda phage DNA segments and their propagation in cultured monkey cells".

9768:"RCSB PDB – 1RVA: Mg2+ binding to the active site of EcoRV endonuclease: a crystallographic study of complexes with substrate and product DNA at 2 Å resolution" 9442: 14590: 4484:

Irobalieva RN, Fogg JM, Catanese DJ, Catanese DJ, Sutthibutpong T, Chen M, Barker AK, Ludtke SJ, Harris SA, Schmid MF, Chiu W, Zechiedrich L (October 2015).

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repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix. The green spheres in the center represent potassium ions.

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is to claim that cross-contamination of evidence has occurred. This has resulted in meticulous strict handling procedures with new cases of serious crime.

2672:, which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (4 combinations). These encode the twenty 14214: 3295:

DNA contains the genetic information that allows all forms of life to function, grow and reproduce. However, it is unclear how long in the 4-billion-year

1579:(mtDNA) which encodes certain proteins used by the mitochondria. The mtDNA is usually relatively small in comparison to the nuclear DNA. For example, the 1526:(to scale at bottom left). The blue scale to the left of each chromosome pair (and the mitochondrial genome) shows its length in terms of millions of DNA 11499: 1879: 2442:, which depends on the same interaction between RNA nucleotides. In an alternative fashion, a cell may copy its genetic information in a process called 1319:, but the major and minor grooves are always named to reflect the differences in width that would be seen if the DNA was twisted back into the ordinary 13938:

First published in October 1974 by MacMillan, with foreword by Francis Crick; the definitive DNA textbook, revised in 1994 with a nine-page postscript.

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Johnson TB, Coghill RD (1925). "Pyrimidines. CIII. The discovery of 5-methylcytosine in tuberculinic acid, the nucleic acid of the tubercle bacillus".

2320:. Because of inherent limits in the DNA repair mechanisms, if humans lived long enough, they would all eventually develop cancer. DNA damages that are 1592:

can contain 100,000 mitochondria, corresponding to up to 1,500,000 copies of the mitochondrial genome (constituting up to 90% of the DNA of the cell).

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Schoeffler AJ, Berger JM (December 2005). "Recent advances in understanding structure-function relationships in the type II topoisomerase mechanism".

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long enough, it is inevitable that at least one of his or her cells would eventually accumulate a set of mutations sufficient for cancer to develop.

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Luger K, Mäder AW, Richmond RK, Sargent DF, Richmond TJ (September 1997). "Crystal structure of the nucleosome core particle at 2.8 A resolution".

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Vreeland RH, Rosenzweig WD, Powers DW (October 2000). "Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal".

993:(five prime end) carbons, the prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a 6334: 6289: 5232:

Wing R, Drew H, Takano T, Broka C, Tanaka S, Itakura K, Dickerson RE (October 1980). "Crystal structure analysis of a complete turn of B-DNA".

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Griffith JD, Comeau L, Rosenfield S, Stansel RM, Bianchi A, Moss H, de Lange T (May 1999). "Mammalian telomeres end in a large duplex loop".

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typically contain few genes but are important for the function and stability of chromosomes. An abundant form of noncoding DNA in humans are

2153:

protein core around which DNA is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see

10999: 6889: 6579: 5429:"A more unified picture for the thermodynamics of nucleic acid duplex melting: a characterization by calorimetric and volumetric techniques" 3042:

break, before rejoining the helix. Topoisomerases are required for many processes involving DNA, such as DNA replication and transcription.

3246:

Recombination allows chromosomes to exchange genetic information and produces new combinations of genes, which increases the efficiency of

2867:. These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to 13432: 5197:

Carell T, Kurz MQ, Müller M, Rossa M, Spada F (April 2018). "Non-canonical Bases in the Genome: The Regulatory Information Layer in DNA".

1749:

that provided only a limited amount of structural information for oriented fibers of DNA. An alternative analysis was proposed by Wilkins

9535:

Grosschedl R, Giese K, Pagel J (March 1994). "HMG domain proteins: architectural elements in the assembly of nucleoprotein structures".

2875:

A distinct group of DNA-binding proteins is the DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication

1903:

region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This

1386:

In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called

14615: 12526: 5841: 488: 11544: 11310: 4326: 3277:

or damage to the DNA. A series of steps catalyzed in part by the recombinase then leads to joining of the two helices by at least one

2141:. Base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of 799:, these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. 14788: 9029:

Whitchurch CB, Tolker-Nielsen T, Ragas PC, Mattick JS (February 2002). "Extracellular DNA required for bacterial biofilm formation".

7904:

Cadet J, Delatour T, Douki T, Gasparutto D, Pouget JP, Ravanat JL, Sauvaigo S (March 1999). "Hydroxyl radicals and DNA base damage".

4983: 3143:

at the ends of chromosomes. Telomeres prevent fusion of the ends of neighboring chromosomes and protect chromosome ends from damage.

10847:

Nickle DC, Learn GH, Rain MW, Mullins JI, Mittler JE (January 2002). "Curiously modern DNA for a "250 million-year-old" bacterium".

8040: 6816: 6648: 6404: 3123:

RNA-dependent DNA polymerases are a specialized class of polymerases that copy the sequence of an RNA strand into DNA. They include

2903:

In contrast, other proteins have evolved to bind to particular DNA sequences. The most intensively studied of these are the various

5732: 3944: 2496:. The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its 1472:

content have more weakly interacting strands. In biology, parts of the DNA double helix that need to separate easily, such as the

15175: 14737: 3654:

relationships and protein function. Data sets representing entire genomes' worth of DNA sequences, such as those produced by the

8718:

Harrison PM, Gerstein M (May 2002). "Studying genomes through the aeons: protein families, pseudogenes and proteome evolution".

7852: 4612: 3736:, synthetic oligonucleotide ligands for specific target molecules used in a range of biotechnology and biomedical applications. 3108:

activity is activated and the incorrect base removed. In most organisms, DNA polymerases function in a large complex called the

13664: 2770:

is found in the blood of the mother, and can be sequenced to determine a great deal of information about the developing fetus.

2641:

sequence, which then defines one or more protein sequences. The relationship between the nucleotide sequences of genes and the

2182:

have higher levels, with up to 1% of their DNA containing 5-methylcytosine. Despite the importance of 5-methylcytosine, it can

4756: 1185:

A number of noncanonical bases are known to occur in DNA. Most of these are modifications of the canonical bases plus uracil.

990: 986: 892: 888: 14956: 14125: 14080: 14057: 14016: 13997: 13410: 13394: 13306: 12823:

From page 313: "I think that the size of the chromosomes in the salivary glands is determined through the multiplication of

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Koltzoff NK (1928). "Physikalisch-chemische Grundlagen der Morphologie" [The physical-chemical basis of morphology].

11818: 11781: 11201: 11022: 9476: 8821: 8107: 5763:

Satoh M, Kuroiwa T (September 1991). "Organization of multiple nucleoids and DNA molecules in mitochondria of a human cell".

4962: 4320: 4125: 3087:

group at the end of the growing polynucleotide chain. As a consequence, all polymerases work in a 5′ to 3′ direction. In the

6472: 4128:. Nobel Prizes are awarded only to living recipients. A debate continues about who should receive credit for the discovery. 3724:

have also been demonstrated, and these DNA structures have been used to template the arrangement of other molecules such as

14595: 11055: 9066:"DNA builds and strengthens the extracellular matrix in Myxococcus xanthus biofilms by interacting with exopolysaccharides" 4139:. Further work by Crick and co-workers showed that the genetic code was based on non-overlapping triplets of bases, called 4088: 4075: 2240: 772:, where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes 4470: 2421:

has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the

15622: 14439: 14367: 8076: 4349: 1994:

Several artificial nucleobases have been synthesized, and successfully incorporated in the eight-base DNA analogue named

1410:(hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. As hydrogen bonds are not 1387: 13050: 10234:

Cremer T, Cremer C (April 2001). "Chromosome territories, nuclear architecture and gene regulation in mammalian cells".

1882:, telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence. 14820: 14610: 14404: 11525: 8596:"RCSB PDB – 1MSW: Structural basis for the transition from initiation to elongation transcription in T7 RNA polymerase" 4672:

Arrighi, Frances E.; Mandel, Manley; Bergendahl, Janet; Hsu, T. C. (June 1970). "Buoyant densities of DNA of mammals".

4132: 1812: 1002: 14373:

Seven-page, handwritten letter that Crick sent to his 12-year-old son Michael in 1953 describing the structure of DNA.

12982:

Brachet J (1933). "Recherches sur la synthese de l'acide thymonucleique pendant le developpement de l'oeuf d'Oursin".

12616: 5893:

Munroe SH (November 2004). "Diversity of antisense regulation in eukaryotes: multiple mechanisms, emerging patterns".

1664:. These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as 15261: 14928: 14147: 14106: 14038: 13931: 13909: 13887: 13866: 13847: 11888: 8070: 7665: 4739: 4456: 4426: 4401: 3872:("tetranucleotide hypothesis"). Levene thought the chain was short and the bases repeated in a fixed order. In 1927, 1009:, the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are 2781:, monitoring the movements and presence of species in water, air, or on land, and assessing an area's biodiversity. 2287:. The type of DNA damage produced depends on the type of mutagen. For example, UV light can damage DNA by producing 15548: 14372: 9403: 8310:

Braña MF, Cacho M, Gradillas A, de Pascual-Teresa B, Ramos A (November 2001). "Intercalators as anticancer drugs".

7150:

Parkinson GN, Lee MP, Neidle S (June 2002). "Crystal structure of parallel quadruplexes from human telomeric DNA".

3375: 2795:

Neutrophil extracellular traps (NETs) are networks of extracellular fibers, primarily composed of DNA, which allow

2321: 2215: 14318: 14257: 12755:] (Speech). 3rd All-Union Meeting of Zoologist, Anatomists, and Histologists (in Russian). Leningrad, U.S.S.R. 12546: 8669:

Harrison PM, Hegyi H, Balasubramanian S, Luscombe NM, Bertone P, Echols N, Johnson T, Gerstein M (February 2002).

2035:

which leave behind negative charges on the phosphate groups. These negative charges protect DNA from breakdown by

15553: 15082: 15026: 14164: 13268: 13078: 2992: 2847:, while in prokaryotes multiple types of proteins are involved. The histones form a disk-shaped complex called a 2161:

between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression.

114:

encode genes, which provide functions. A human DNA can have up to 500 million base pairs with thousands of genes.

13323: 10320:

O'Driscoll M, Jeggo PA (January 2006). "The role of double-strand break repair – insights from human genetics".

10061: 8671:"Molecular fossils in the human genome: identification and analysis of the pseudogenes in chromosomes 21 and 22" 6842: 6109: 2911:

that modify the histones at the promoter. This changes the accessibility of the DNA template to the polymerase.

725:

to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, the single-ringed

15021: 2790: 2406: 481: 13143:

Chargaff E (June 1950). "Chemical specificity of nucleic acids and mechanism of their enzymatic degradation".

12761:

Koltsov HK (1928). "Физико-химические основы морфологии" [The physical-chemical basis of morphology].

11503: 361: 15450: 15336: 15109: 15040: 14781: 11834:

Sjölander K (January 2004). "Phylogenomic inference of protein molecular function: advances and challenges".

11399:

Weir BS, Triggs CM, Starling L, Stowell LI, Walsh KA, Buckleton J (March 1997). "Interpreting DNA mixtures".

8804:

Tani K, Nasu M (2010). "Roles of Extracellular DNA in Bacterial Ecosystems". In Kikuchi Y, Rykova EY (eds.).

6934: 4136: 2562: 8095: 2595:, which are copies of genes that have been disabled by mutation. These sequences are usually just molecular 14845: 14696: 12396:

Dahm R (January 2008). "Discovering DNA: Friedrich Miescher and the early years of nucleic acid research".

10078:

Johnson A, O'Donnell M (2005). "Cellular DNA replicases: components and dynamics at the replication fork".

4757:"Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents. Recommendations 1970" 4022: 3816: 3428: 3258: 2673: 2329: 1580: 1523: 1381:

base pair with two hydrogen bonds. Non-covalent hydrogen bonds between the pairs are shown as dashed lines.

42: 13269:"Pictures and Illustrations: Crystallographic photo of Sodium Thymonucleate, Type B. "Photo 51." May 1952" 10363:

Vispé S, Defais M (October 1997). "Mammalian Rad51 protein: a RecA homologue with pleiotropic functions".

8539:"Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project" 3568:

methods happen after birth, but there are new methods to test paternity while a mother is still pregnant.

2149:

bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the

15563: 15558: 15543: 15168: 14376: 8931:"Extracellular DNA chelates cations and induces antibiotic resistance in Pseudomonas aeruginosa biofilms" 5530: 4258: 4162:

In 1986, DNA analysis was first used for criminal investigative purposes when police in the UK requested

4062: 3647: 2799:, a type of white blood cell, to kill extracellular pathogens while minimizing damage to the host cells. 1029: 1010: 753: 13487: 7477: 6489:

Leslie AG, Arnott S, Chandrasekaran R, Ratliff RL (October 1980). "Polymorphism of DNA double helices".

1870:. The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme 15596: 15060: 14444: 12787:

In 1934, Koltsov contended that the proteins that contain a cell's genetic information replicate. See:

12323:

Akram F, Haq IU, Ali H, Laghari AT (October 2018). "Trends to store digital data in DNA: an overview".

11810: 10898:

Callahan MP, Smith KE, Cleaves HJ, Ruzicka J, Stern JC, Glavin DP, House CH, Dworkin JP (August 2011).

10455:

Dickman MJ, Ingleston SM, Sedelnikova SE, Rafferty JB, Lloyd RG, Grasby JA, Hornby DP (November 2002).

6670:

Lu XJ, Shakked Z, Olson WK (July 2000). "A-form conformational motifs in ligand-bound DNA structures".

3856:

of discarded surgical bandages. As it resided in the nuclei of cells, he called it "nuclein". In 1878,

3623: 2223: 2137:

The expression of genes is influenced by how the DNA is packaged in chromosomes, in a structure called

1490:

In the laboratory, the strength of this interaction can be measured by finding the melting temperature

1165: 250: 10958: 9174:"Investigating the potential use of environmental DNA (eDNA) for genetic monitoring of marine mammals" 1080:). These four bases are attached to the sugar-phosphate to form the complete nucleotide, as shown for 14600: 14585: 14360:

Another DNA Learning Center site on DNA, genes, and heredity from Mendel to the human genome project.

14249: 4289: 4234: – Universal notation using the Roman characters A, C, G, and T to call the four DNA nucleotides 4152: 3452: 3436: 3262: 3079:. The sequence of their products is created based on existing polynucleotide chains—which are called 2313: 2276: 2008: 1601: 1006: 938:(which interacts with the other DNA strand in the helix). A nucleobase linked to a sugar is called a 749: 612: 474: 12789:

Koltzoff N (October 1934). "The structure of the chromosomes in the salivary glands of Drosophila".

12743:

Koltsov proposed that a cell's genetic information was encoded in a long chain of amino acids. See:

10569: 9304:"The role of nucleoid-associated proteins in the organization and compaction of bacterial chromatin" 8240:

Stephens TD, Bunde CJ, Fillmore BJ (June 2000). "Mechanism of action in thalidomide teratogenesis".

7215: 6302:"The structure of sodium thymonucleate fibres. II. The cylindrically symmetrical Patterson function" 6301: 6256: 3520:

to identify a matching DNA of an individual, such as a perpetrator. This process is formally termed

2504:

and is a region of DNA that influences a particular characteristic in an organism. Genes contain an

1437:(low pH also melts DNA, but since DNA is unstable due to acid depurination, low pH is rarely used). 717:. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to 15104: 14892: 14805: 14774: 14605: 14424: 11848: 10812:

Hebsgaard MB, Phillips MJ, Willerslev E (May 2005). "Geologically ancient DNA: fact or artefact?".

3940: 3882: 3860:

isolated the non-protein component of "nuclein", nucleic acid, and later isolated its five primary

3784: 3254: 2920: 2756: 2624: 1714: 1665: 769: 268: 22: 13597: 1894:

structure. These structures are stabilized by hydrogen bonding between the edges of the bases and

15065: 14882: 14867: 13386: 12134:

Aldaye FA, Palmer AL, Sleiman HF (September 2008). "Assembling materials with DNA as the guide".

11972: 10989: 8534: 8162:

Freitas AA, de Magalhães JP (2011). "A review and appraisal of the DNA damage theory of ageing".

7499: 6873: 6610: 4629:

Mandelkern M, Elias JG, Eden D, Crothers DM (October 1981). "The dimensions of DNA in solution".

4030: 4006: 3686: 3163:, the enzyme that transcribes most of the genes in the human genome, operates as part of a large 3076: 3053: 2843:. In eukaryotes, this structure involves DNA binding to a complex of small basic proteins called 2536: 2430: 2191: 1890:, form a flat plate. These flat four-base units then stack on top of each other to form a stable 1775:

analysis of the DNA X-ray diffraction patterns to suggest that the structure was a double helix.

1772: 1759:

B-DNA X-ray diffraction-scattering patterns of highly hydrated DNA fibers in terms of squares of

1685: 1081: 713:) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating 9064:

Hu W, Li L, Sharma S, Wang J, McHardy I, Lux R, Yang Z, He X, Gimzewski JK, Li Y, Shi W (2012).

3685:

The DNA structure at left (schematic shown) will self-assemble into the structure visualized by

3315:

where nucleic acid would have been used for both catalysis and genetics may have influenced the

2492:. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the 15725: 15715: 15583: 15276: 15161: 15070: 14995: 14887: 14397: 14345: 13897: 13003:"Jean Brachet's Cytochemical Embryology: Connections with the Renovation of Biology in France?" 11843: 10564: 8486:"The C-value enigma in plants and animals: a review of parallels and an appeal for partnership" 7210: 5936:

Makalowska I, Lin CF, Makalowski W (February 2005). "Overlapping genes in vertebrate genomes".

3836:, co-originators of the double-helix model based on the X-ray diffraction data and insights of 3228: 3101: 3057: 3000: 2174: 785: 13749: 13578: 13012:. Cahiers pour I'histoire de la recherche. Vol. 2. Paris: CNRS Editions. pp. 207–20. 12841:

Soyfer VN (September 2001). "The consequences of political dictatorship for Russian science".

12507: 12477: 12460: 12443: 12367: 11712:"In vitro selection of a sodium-specific DNAzyme and its application in intracellular sensing" 8813: 2991:

infection by digesting the phage DNA when it enters the bacterial cell, acting as part of the

15460: 15304: 14985: 14970: 14850: 14732: 14566: 14531: 14188: 10091: 10041: 6964:"Identification of a specific telomere terminal transferase activity in Tetrahymena extracts" 4898:"Base-stacking and base-pairing contributions into thermal stability of the DNA double helix" 4237: 4231: 3702: 3694: 3615: 3561: 3296: 3243:

occurs. Chromosomal crossover is when two DNA helices break, swap a section and then rejoin.

3240: 3232: 3210: 3176: 3156: 3124: 3023: 2646: 2531:

encodes protein. For example, only about 1.5% of the human genome consists of protein-coding

2439: 1989: 1515: 1144: 1116: 761: 441: 421: 386: 298: 293: 12523: 9570:

Iftode C, Daniely Y, Borowiec JA (1999). "Replication protein A (RPA): the eukaryotic SSB".

8805: 5838: 3924:

produced the first X-ray diffraction patterns that showed that DNA had a regular structure.

15495: 15478: 15309: 15092: 14990: 14908: 14631: 14449: 14245: 13958: 13703: 13612: 13534: 13335: 12798: 12143: 12100: 12039: 11987: 11723: 11455: 11353: 11097: 10911: 10856: 10770: 10719: 10664: 10513: 10411: 9720: 9607:"RCSB PDB – 1LMB: Refined 1.8 Å crystal structure of the lambda repressor-operator complex" 9360: 9185: 9077: 8550: 8448: 8358: 8171: 7913: 7702: 7691:"The nuclear DNA base 5-hydroxymethylcytosine is present in Purkinje neurons and the brain" 7434: 7367: 7316: 7159: 6761: 6594: 6440: 6372: 6316: 6271: 6089: 5690: 5645: 5440: 5383: 5241: 4979: 4828: 4572: 4497: 4310: 4079: 4002: 3983: 3760: 3655: 3418: 3312: 3290: 2904: 2868: 2808: 2628: 2154: 2077: 1506: 1311: 1041: 107: 26: 12060: 8982:"A bacterial extracellular DNA inhibits settling of motile progeny cells within a biofilm" 8030: 7572:

Klose RJ, Bird AP (February 2006). "Genomic DNA methylation: the mark and its mediators".

6808: 4085:

in Cambridge, England to announce that he and Watson had "discovered the secret of life".

3767:

can learn the history of particular populations. This can be used in studies ranging from

8: 15490: 15473: 15331: 15214: 14918: 14711: 14701: 14661: 14561: 14541: 14434: 14429: 14178: 7352:

Hoshika S, Leal NA, Kim MJ, Kim MS, Karalkar NB, Kim HJ, et al. (22 February 2019).

6357: 3952: 3932: 3768: 3764: 3529: 3464: 3451:

is a man-made DNA sequence that has been assembled from other DNA sequences. They can be

3422: 3236: 3159:, where it halts and detaches from the DNA. As with human DNA-dependent DNA polymerases, 2964: 2916: 2821: 2767: 2608: 2517: 2509: 2309: 2292: 2158: 1904: 1407: 1147:

have been created to study the properties of nucleic acids, or for use in biotechnology.

978: 860: 733:. In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. 710: 416: 396: 331: 288: 282: 273: 245: 123: 82: 59: 13962: 13707: 13616: 13538: 13339: 13002: 12802: 12147: 12104: 12043: 11991: 11727: 11459: 11357: 11101: 10915: 10860: 10774: 10723: 10668: 10517: 10415: 10165:

Martinez E (December 2002). "Multi-protein complexes in eukaryotic gene transcription".

9724: 9364: 9271: 9246: 9189: 9172:

Foote AD, Thomsen PF, Sveegaard S, Wahlberg M, Kielgast J, Kyhn LA, et al. (2012).

9081: 8626:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

8554: 8452: 8362: 8345:

Venter JC, Adams MD, Myers EW, Li PW, Mural RJ, Sutton GG, et al. (February 2001).

8175: 7917: 7706: 7438: 7371: 7320: 7163: 6765: 6598: 6444: 6376: 6320: 6275: 5736: 5694: 5649: 5632:

Gregory SG, Barlow KF, McLay KE, Kaul R, Swarbreck D, Dunham A, et al. (May 2006).

5444: 5387: 5299: 5245: 4832: 4576: 4501: 3037:

are enzymes with both nuclease and ligase activity. These proteins change the amount of

2834:(in blue). These proteins' basic amino acids bind to the acidic phosphate groups on DNA. 1017:

is the sugar, with the 2-deoxyribose in DNA being replaced by the related pentose sugar

175: 15384: 15379: 15254: 15053: 14936: 14671: 14556: 14551: 14526: 14350: 13804: 13787: 13638: 13560: 13492: 13358: 13245: 13220: 13168: 13120: 13095: 12910: 12885: 12866: 12592: 12575: 12421: 12348: 12300: 12275: 12167: 12073: 12011: 11953: 11807:

Algorithms on Strings, Trees, and Sequences: Computer Science and Computational Biology

11746: 11711: 11646: 11621: 11481: 11424: 11251: 11226: 11166: 10934: 10899: 10880: 10794: 10743: 10633: 10590: 10537: 10486: 10432: 10399: 10345: 10302: 10259: 10190: 10147: 10053: 9434: 9384: 9333: 9284: 9208: 9173: 9149: 9124: 9100: 9065: 9006: 8981: 8957: 8930: 8862: 8646: 8621: 8571: 8538: 8510: 8485: 8035: 7831: 7772: 7747: 7723: 7690: 7549: 7522: 7458: 7424: 7388: 7353: 7280: 7255: 7236: 7183: 7127: 7102: 6916: 6730: 6718: 6545: 6464: 6396: 6200: 6154: 6101: 6046: 6021: 5949: 5918: 5816: 5799: 5714: 5609: 5582: 5511: 5499: 5404: 5371: 5347: 5322: 5265: 5174: 5139: 4930: 4897: 4789: 4705: 4604: 4526: 4485: 4144: 3878: 3849: 3690: 3676: 3635: 3432: 3265:

and genetic abnormalities. The recombination reaction is catalyzed by enzymes known as

2980: 2942: 2513: 2505: 2480:, to fit the small available volumes of the cell. In eukaryotes, DNA is located in the 1924: 1746: 1480: 1174: 1169:

in 1925. The reason for the presence of these noncanonical bases in bacterial viruses (

411: 406: 381: 303: 14095: 13726: 13691: 13204: 13187: 12959: 12934: 12695: 12678: 12251: 12224: 11940: 11913: 11687: 11670: 11287: 11242: 11056:"World's oldest DNA sequenced from a mammoth that lived more than a million years ago" 10376: 9998: 9973: 9870: 9845: 9818: 9793: 9743: 9708: 8906: 8881: 8781: 8754: 8731: 8695: 8670: 8253: 7925: 7412: 7224: 7075: 7050: 6784: 6749: 6175:

Wang JC (June 2002). "Cellular roles of DNA topoisomerases: a molecular perspective".

5997: 5972: 5395: 4754: 2291:, which are cross-links between pyrimidine bases. On the other hand, oxidants such as 15468: 15430: 15423: 15374: 15326: 14755: 14686: 14676: 14666: 14500: 14390: 14334: 14143: 14121: 14102: 14076: 14069: 14053: 14034: 14012: 13993: 13976: 13927: 13905: 13883: 13862: 13843: 13809: 13731: 13630: 13564: 13552: 13390: 13363: 13302: 13295: 13250: 13160: 13125: 13070: 12964: 12915: 12858: 12814: 12726: 12597: 12413: 12340: 12305: 12256: 12159: 12116: 12065: 12003: 11945: 11894: 11884: 11861: 11814: 11787: 11777: 11751: 11692: 11651: 11602: 11598: 11552: 11473: 11416: 11381: 11376: 11341: 11291: 11256: 11207: 11197: 11158: 11154: 11123: 11115: 10939: 10872: 10829: 10786: 10735: 10692: 10687: 10652: 10625: 10582: 10529: 10478: 10473: 10456: 10437: 10380: 10337: 10294: 10251: 10182: 10139: 10095: 10045: 10003: 9989: 9954: 9949: 9910: 9875: 9823: 9748: 9689: 9648: 9644: 9587: 9552: 9548: 9517: 9482: 9472: 9426: 9376: 9325: 9320: 9303: 9276: 9213: 9154: 9105: 9046: 9011: 8997: 8962: 8911: 8897: 8854: 8817: 8806: 8786: 8735: 8700: 8651: 8576: 8515: 8466: 8417: 8376: 8327: 8292: 8288: 8257: 8222: 8218: 8187: 8144: 8103: 8066: 8011: 7970: 7929: 7886: 7849: 7823: 7809: 7777: 7728: 7671: 7661: 7630: 7589: 7554: 7450: 7393: 7358: 7334: 7285: 7228: 7175: 7132: 7080: 7031: 6985: 6980: 6963: 6903:

Cressey D (3 October 2012). "'Arsenic-life' Bacterium Prefers Phosphorus after all".

6789: 6722: 6687: 6652: 6549: 6506: 6502: 6456: 6388: 6235: 6204: 6192: 6146: 6142: 6093: 6051: 6037: 6002: 5953: 5910: 5875: 5821: 5780: 5776: 5706: 5663: 5614: 5553: 5503: 5468: 5463: 5428: 5409: 5352: 5303: 5257: 5214: 5179: 5161: 5120: 5112: 5071: 5036: 5028: 4958: 4935: 4917: 4852: 4844: 4794: 4776: 4735: 4697: 4689: 4654: 4646: 4642: 4596: 4588: 4557: 4531: 4513: 4462: 4452: 4422: 4397: 4390: 4316: 4267: 4213: 4156: 4045: 4041: 3837: 3749: 3639: 3414: 3332: 3278: 3247: 3206: 3160: 2996: 2976: 2774: 2735: 2572: 2305: 2296: 1576: 832: 461: 346: 225: 15137: 14354:, June 1953. First American newspaper coverage of the discovery of the DNA structure 14303: 13837: 13673: 13221:"Independent functions of viral protein and nucleic acid in growth of bacteriophage" 12870: 12711: 12352: 12241: 11957: 11857: 11428: 11170: 10884: 10637: 10490: 10306: 10194: 10151: 10057: 9337: 9288: 8866: 8771: 7835: 7462: 6920: 6734: 6158: 5922: 5858:

Hüttenhofer A, Schattner P, Polacek N (May 2005). "Non-coding RNAs: hope or hype?".

5515: 5023: 5006: 4709: 3362:, have also been formed in the laboratory under conditions mimicking those found in 2633:

A gene is a sequence of DNA that contains genetic information and can influence the

2557:". However, some DNA sequences that do not code protein may still encode functional 2190:. Other base modifications include adenine methylation in bacteria, the presence of 15720: 15294: 14716: 14691: 14313: 14283: 14268: 13966: 13799: 13721: 13711: 13642: 13620: 13542: 13525: 13353: 13343: 13240: 13232: 13199: 13172: 13152: 13115: 13107: 13042: 12954: 12950: 12946: 12905: 12897: 12850: 12806: 12690: 12659: 12628: 12587: 12405: 12332: 12295: 12287: 12246: 12236: 12198: 12171: 12151: 12108: 12077: 12055: 12047: 12015: 11995: 11935: 11925: 11853: 11741: 11731: 11682: 11641: 11633: 11594: 11485: 11463: 11408: 11371: 11361: 11283: 11246: 11238: 11189: 11150: 11105: 11088: 10929: 10919: 10864: 10821: 10798: 10778: 10747: 10727: 10682: 10672: 10621: 10617: 10594: 10574: 10541: 10521: 10468: 10427: 10419: 10372: 10349: 10329: 10286: 10263: 10243: 10174: 10129: 10087: 10037: 9993: 9985: 9944: 9902: 9865: 9857: 9813: 9809: 9805: 9738: 9728: 9679: 9640: 9579: 9544: 9509: 9464: 9438: 9418: 9388: 9368: 9315: 9266: 9258: 9203: 9193: 9144: 9136: 9095: 9085: 9038: 9001: 8993: 8952: 8942: 8901: 8893: 8846: 8776: 8766: 8727: 8690: 8682: 8641: 8633: 8566: 8558: 8505: 8497: 8456: 8407: 8366: 8319: 8284: 8249: 8214: 8179: 8136: 8001: 7960: 7921: 7878: 7813: 7805: 7767: 7759: 7718: 7710: 7653: 7620: 7581: 7544: 7534: 7442: 7383: 7375: 7324: 7275: 7267: 7220: 7187: 7167: 7122: 7114: 7070: 7062: 7021: 6975: 6908: 6881: 6779: 6769: 6714: 6679: 6644: 6602: 6537: 6498: 6468: 6448: 6400: 6380: 6324: 6279: 6231: 6227: 6184: 6138: 6105: 6085: 6041: 6033: 5992: 5984: 5945: 5902: 5867: 5811: 5772: 5718: 5698: 5653: 5604: 5594: 5545: 5495: 5458: 5448: 5399: 5391: 5342: 5334: 5295: 5269: 5249: 5206: 5169: 5151: 5102: 5063: 5018: 4925: 4909: 4836: 4802: 4784: 4768: 4681: 4638: 4608: 4580: 4521: 4505: 4207: 4148: 4098: 4026: 3974: 3627: 3619: 3493: 3472: 3343: 3015: 3011: 2896: 2715: 2711: 2707: 2604: 2477: 2435: 2338: 2172:

of chromosomes. The average level of methylation varies between organisms—the worm

2165: 2114: 1822: 1631: 1156: 1139:), usually takes the place of thymine in RNA and differs from thymine by lacking a 671: 632: 507: 353: 140: 14278: 13418: 12425: 12186: 10210:"RCSB PDB – 1M6G: Structural Characterisation of the Holliday Junction TCGGTACCGA" 9042: 7652:. Current Topics in Microbiology and Immunology. Vol. 301. pp. 283–315. 7240: 4363: 4140: 2637:

of an organism. Within a gene, the sequence of bases along a DNA strand defines a

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Lindahl T (April 1993). "Instability and decay of the primary structure of DNA".

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Pál C, Papp B, Lercher MJ (May 2006). "An integrated view of protein evolution".

10118:"The reverse transcriptase of HIV-1: from enzymology to therapeutic intervention" 10116:

Tarrago-Litvak L, Andréola ML, Nevinsky GA, Sarih-Cottin L, Litvak S (May 1994).

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In 1962, after Franklin's death, Watson, Crick, and Wilkins jointly received the

4053: 4037: 3921: 3886: 3873: 3857: 3841: 3802: 3794: 3659: 3631: 3549: 3541: 3448: 3300: 3273:. The first step in recombination is a double-stranded break caused by either an 3164: 3049: 2860: 2731: 2685: 2443: 2327:

Many mutagens fit into the space between two adjacent base pairs, this is called

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when the two strands separate. A large part of DNA (more than 98% for humans) is

741: 702: 662:

The two DNA strands are known as polynucleotides as they are composed of simpler

13046: 13028:"Some recent developments in the X-ray study of proteins and related structures" 12810: 12480:[On the distribution of hypoxanthins in the animal and plant kingdoms]. 11710:

Torabi SF, Wu P, McGhee CE, Chen L, Hwang K, Zheng N, Cheng J, Lu Y (May 2015).

11193: 9709:"A global transcriptional regulatory role for c-Myc in Burkitt's lymphoma cells" 9468: 9247:"Diversity of prokaryotic chromosomal proteins and the origin of the nucleosome" 8837:

Vlassov VV, Laktionov PP, Rykova EY (July 2007). "Extracellular nucleic acids".

8183: 6257:"The Structure of Sodium Thymonucleate Fibres I. The Influence of Water Content" 5581:

Piovesan A, Pelleri MC, Antonaros F, Strippoli P, Caracausi M, Vitale L (2019).

5107: 5090: 4558:"Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid" 4052:", at high hydration levels of DNA. This photo was given to Watson and Crick by 3797:

compared to electronic devices. However, high costs, slow read and write times (

3528:. In DNA profiling, the lengths of variable sections of repetitive DNA, such as 1028:

A section of DNA. The bases lie horizontally between the two spiraling strands (

15610: 15510: 15413: 15230: 14941: 14913: 14706: 14646: 14546: 13696: