Space-filling model of a section of DNA molecule

Deoxyribonucleic acid (DNA) or deoxyribose nucleic acid is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). DNA is often referred to as the molecule of heredity, as it is responsible for the genetic propagation of most inherited traits. During reproduction, DNA is replicated and transmitted to the offspring. Download high resolution version (313x821, 111 KB)Image of the DNA double-helix in a space filling model This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ... Download high resolution version (313x821, 111 KB)Image of the DNA double-helix in a space filling model This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ... A nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... An instruction is a form of information which is communicated in order to explain how an action, behavior, method, or task is to be begun, completed, conducted, or executed. ... Developmental biology is the study of the process by which organisms grow and develop. ... This article concerns the primary meanings of life in biology. ... Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... For the scientific journal Heredity see Heredity (journal) Heredity (the adjective is hereditary) is the transfer of characters from parent to offspring, either through their genes or through the social institution called inheritance (for example, a title of nobility is passed from individual to individual according to relevant customs and... Biological inheritance is the process by which an offspring cell or organism acquires or becomes predisposed to characteristics of its parent cell or organism. ... In biology, a trait or character is a genetically inherited feature of an organism. ... Reproduction is the creation of one thing as a copy of, product of, or replacement for a similar thing, e. ... DNA replication. ...

In bacteria and other simple cell organisms, DNA is not separated from the cytoplasm by a nuclear envelope. In the complex cells that make up plants, animals and in other multi-cellular organisms, by contrast, most of the DNA is located in the cell nucleus. The energy-generating organelles known as chloroplasts and mitochondria also carry DNA, as do many viruses. Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Cells in culture, stained for keratin The cell is the structural and functional unit of all living organisms. ... Cytoplasm is the colloidal, semi-fluid matter contained within the cells plasma membrane, in which organelles are suspended. ... The nuclear envelope refers to the double membrane of the nucleus that encloses genetic material in eukaryotic cells. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Divisions Green algae land plants (embryophytes) non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses vascular plants (tracheophytes) seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongue ferns seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa Myxozoa Superphylum Deuterostomia    Chordata (vertebrates, etc. ... In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... In cell biology, the nucleus (from Latin nucleus or nuculeus, kernel) is an organelle, found in all eukaryotic cells, which contains most of the cells genetic material. ... In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ... Chloroplasts are organelles found in plant cells and eukaryotic algae which conduct photosynthesis. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). ...

DNA in brief

This section presents a brief and simple overview of DNA. General science-related image. ... Some unsolved problems in biology include: Life. ...

• Genes can be loosely viewed as the organism's "cookbook";
• A strand of DNA contains genes, areas that regulate genes, and areas that either have no function, or a function we do not (yet) know;
• DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands;
• DNA is encoded with four interchangeable "building blocks", called "bases", which can be abbreviated A, T, C, and G; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand;
• The order does matter: A+T is not the same as T+A, just as C+G is not the same as G+C;
• However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence;
• The order of the bases along the length of the DNA is what it's all about, the sequence itself is the description for genes;
• Replication is performed by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs;
• Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations".

This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Gene regulation is the general term for cellular control of protein synthesis at the DNA-RNA transcription step. ... Within a chromosome or a genome, the junk DNA are those portions of the DNA for which no function has been identified. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... Adenine is one of the two purine nucleobases used in forming nucleotides of the nucleic acids DNA and RNA. In DNA, adenine (A) binds to thymine (T) to assist in stabilizing the nucleic acid structures. ... Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... Cytosine Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell. ... Guanine is one of the four main nucleobases found in nucleic acids (e. ... 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, thymine), and typically these are... DNA replication. ... This article is about mutation in biology, for other meanings see: mutation (disambiguation). ...

DNA in crime

Forensic scientists can use DNA located in blood, semen, or hair left at the scene of a crime to identify a possible suspect, a process called DNA profiling or genetic fingerprinting. In DNA profiling the relative lengths of sections of repetitive DNA, such as short tandem repeats and minisatellites, are compared. DNA profiling was developed in 1984 by English geneticist Alec Jeffries, and was first used in 1986 in the Enderby murders case in Leicestershire, England. Many jurisdictions require convicts of certain types of crimes to provide a sample of DNA for inclusion in a computerized database. This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers). This method is one of the most reliable techniques for identifying a criminal, but is not always perfect, for example if no DNA can be retrieved, or if the scene is contaminated with the DNA of several possible suspects. Forensics or forensic science is the application of science to questions which are of interest to the legal system. ... Genetic fingerprinting or DNA testing is a technique to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. ... The short tandem repeats (STR) are tandemly repeated DNA sequences of a pattern of length from 2 to 10 bp (for example (CA)n(TG)n in a genomics region) and the total size is lower than 100 bp. ... 1984 is a leap year starting on Sunday of the Gregorian calendar. ... Sir Alec J. Jeffreys, FRS, (born in 1950 at Luton in Bedfordshire) is a British scientist and professor. ... 1986 is a common year starting on Wednesday of the Gregorian calendar. ... Colin Pitchfork Colin Pitchfork (born c. ... Leicestershire (abbreviated Leics) is a landlocked county in central England. ... Royal motto: Dieu et mon droit (French: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831 377/km² Religion...

Overview of molecular structure

Schematic representation of the DNA which illustrates its double helix structure

Although sometimes called "the molecule of heredity", pieces of DNA as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right). This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... The Double-Helix are an alien race in the Wing Commander science fiction series. ... This article is about the shape. ...

Each vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar, a phosphate and one of four kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers. A nucleotide is an organic molecule consisting of a heterocyclic nucleobase (a purine or a pyrimidine), a pentose sugar (deoxyribose in DNA or ribose in RNA), and a phosphate or polyphosphate group. ... A sugar is a form of carbohydrate; the most commonly used sugar is a white crystalline solid, sucrose; used to alter the flavor and properties (mouthfeel, preservation, texture) of beverages and food. ... In chemistry, a phosphate is a polyatomic ion or radical consisting of one phosphorus atom and four oxygen. ... Nucleobases are the parts of RNA and DNA that are involved in pairing up (see also base pairs). ... A polymer is a generic term used to describe a substantially long molecule. ...

The diversity of the bases means that there are four kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine is one of the two purine nucleobases used in forming nucleotides of the nucleic acids DNA and RNA. In DNA, adenine (A) binds to thymine (T) to assist in stabilizing the nucleic acid structures. ... Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... Cytosine Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell. ... Guanine is one of the four main nucleobases found in nucleic acids (e. ...

In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect. Specificity of which strands stay associated is determined by complementary pairing. Each base forms hydrogen bonds readily to only one other -- A to T and C to G -- so that the identity of the base on one strand dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association. The hydrophobic effect is the property that nonpolar molecules like to self-associate in the presence of aqueous solution. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... http://www. ...

The cell's machinery is capable of melting or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR mimics this process in vitro in a nonliving system. This article is about mutation in biology, for other meanings see: mutation (disambiguation). ... Wikipedia does not yet have an article with this exact name. ...

Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it is chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand.

Download high resolution version (1024x1024, 83 KB) Wikipedia does not have an article with this exact name. ... Animation of a rotating DNA structure. ... A megabyte (derived from the SI prefix mega-) is a unit of information or computer storage equal to one million bytes. ... GIF (Graphics Interchange Format) is a bitmap image format that is widely used on the World Wide Web, both for still images and for animations. ...

The role of the sequence

Within a gene, the sequence of nucleotides along a DNA strand defines a protein, which an organism is liable to manufacture or "express" at one or several points in its life using the information of the sequence. The relationship between the nucleotide sequence and the amino-acid sequence of the protein is determined by simple cellular rules of translation, known collectively as the genetic code. The genetic code is made up of three-letter 'words' (termed a codon) formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid. Since there are 64 possible codons, most amino acids have more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... Gene expression (also protein expression or often simply expression) is the process by which a genes information is converted into the structures and functions of a cell. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Translation in the cytoplasm; tRNA carries amino acids which are added to the growing peptide chain in the ribosome. ... RNA codons. ... RNA codons. ... ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ...

In many species of organism, only a small fraction of the total sequence of the genome appears to encode protein. The function of the rest is a matter of speculation. It is known that certain nucleotide sequences specify affinity for DNA binding proteins, which play a wide variety of vital roles, in particular through control of replication and transcription. These sequences are frequently called regulatory sequences, and researchers assume that so far they have identified only a tiny fraction of the total that exist. "Junk DNA" represents sequences that do not yet appear to contain genes or to have a function. In biology, a species is a kind of organism. ... 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). ... DNA-binding proteins are a broad class of protein molecules that possess certain structural motifs (i. ... A regulatory sequence is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ... Within a chromosome or a genome, the junk DNA are those portions of the DNA for which no function has been identified. ...

Sequence also determines a DNA segment's susceptibility to cleavage by restriction enzymes, the quintessential tools of genetic engineering. The position of cleavage sites throughout an individual's genome determines one kind of an individual's "DNA fingerprint". A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded DNA. The enzyme makes two incisions, one through each of the phosphate backbones of the double helix without damaging the bases. ... An iconic image of genetic engineering; this 1986 autoluminograph of a glowing transgenic tobacco plant bearing the luciferase gene of fireflys strikingly demonstrates the power and potential of genetic manipulation. ... Genetic fingerprinting or DNA testing is a technique to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. ...

DNA replication

Main article: DNA replication DNA replication. ...

DNA replication

DNA replication or DNA synthesis is the process of copying the double-stranded DNA prior to cell division. The two resulting double strands are generally almost perfectly identical, but occasionally errors in replication can result in a less than perfect copy (see mutation), and each of them consists of one original and one newly synthesized strand. This is called semiconservative replication. The process of replication consists of three steps: initiation, replication and termination. DNA replication. ... Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. ... This article is about mutation in biology, for other meanings see: mutation (disambiguation). ... Semiconservative replication describes the method by which DNA is replicated in all known cells. ...

Mechanical properties relevant to biology

Strands association and dissociation

The hydrogen bonds between the strands of the double helix are weak enough that they can be easily separated by enzymes. Enzymes known as helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The strands can also be separated by gentle heating, as used in PCR, provided they have fewer than about 10,000 base pairs (10 kilobase pairs, or 10 kbp). The intertwining of the DNA strands makes long segments difficult to separate. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Helicase is an enzyme vital to all living organisms. ... DNA polymerase 3D structure. ... Wikipedia does not yet have an article with this exact name. ...

Circular DNA

When the ends of a piece of double-helical DNA are joined so that it forms a circle, as in plasmid DNA, the strands are topologically knotted. This means they cannot be separated by gentle heating or by any process that does not involve breaking a strand. The task of unknotting topologically linked strands of DNA falls to enzymes known as topoisomerases. Some of these enzymes unknot circular DNA by cleaving two strands so that another double-stranded segment can pass through. Unknotting is required for the replication of circular DNA as well as for various types of recombination in linear DNA. Figure 1 : Schematic drawing of a bacterium with plasmids enclosed. ... Trefoil knot, the simplest non-trivial knot. ... Topoisomerases (Type I: EC 5. ... Recombination usually denotes a genetic event that occurs during the formation of sperm and egg cells (especially in areas of study of biology topics). ...

Great length versus tiny breadth

The narrow breadth of the double helix makes it impossible to detect by conventional electron microscopy, except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length -- approximately 5 centimetres long for strands in a human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. This is one of the functions of the chromosomes, which contain spool-like proteins known as histones, around which DNA winds. Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is focused onto a specimen causing an enlarged version to appear on a fluorescent screen or layer of photographic film (see electron microscope), or can be detected by a CCD camera. ... A centimetre (American spelling: centimeter, symbol: cm) is an SI unit of length. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In biology, histones are the chief proteins of chromatin. ...

Different helix geometries

The DNA helix can assume one of three slightly different geometries, of which the "B" form described by James D. Watson and Francis Crick is believed to predominate in cells. It is 2 nanometres wide and extends 3.4 nanometres per 10 bp of sequence. This is also the approximate length of sequence in which the double helix makes one complete turn about its axis. This frequency of twist (known as the helical pitch) depends largely on stacking forces that each base exerts on its neighbors in the chain. James Watson James Dewey Watson (born April 6, 1928) is one of the discoverers of the structure of the DNA molecule. ... Photomontage of Francis Crick lecturing Francis Harry Compton Crick, OM (June 8, 1916 – July 28, 2004) was one of the discoverers of the structure of the DNA molecule. ... A nanometre (American spelling: nanometer) is 1. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ...

Supercoiled DNA

The B form of the DNA helix twists 360° per 10.6 bp in the absence of strain. But many molecular biological processes can induce strain. A DNA segment with excess or insufficient helical twisting is referred to, respectively, as positively or negatively "supercoiled". DNA in vivo is typically negatively supercoiled, which facilitates the unwinding of the double-helix required for RNA transcription. In a relaxed double-helical segment of DNA, the two strands twist around the helical axis once every 10. ... Transcription may be one of the following: In linguistics, transcription is the conversion of spoken words into written language. ...

Conditions for formation of A and Z helices

The two other known double-helical forms of DNA, called A and Z, differ modestly in their geometry and dimensions. The A form appears likely to occur only in dehydrated samples of DNA, such as those used in crystallographic experiments, and possibly in hybrid pairings of DNA and RNA strands. Segments of DNA that cells have methylated for regulatory purposes may adopt the Z geometry, in which the strands turn about the helical axis like a mirror image of the B form. Z-DNA is a form of DNA in which the double helix winds to the left in a zig-zag pattern (instead of to the right, like the more common B-DNA form). ... Crystallography (from the Greek words crystallon = solid and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ... Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. ... Methylation refers to the replacement of a hydrogen atom (H) with a methyl group (CH3), regardless of the substrate. ...

Table of comparison of the properties of different helical forms

Non-helical forms

Other, including non-helical, forms of DNA have been described, for example a side-by-side (SBS) configuration. Indeed, it is far from certain that the B-form double helix is the dominant form in living cells.

Direction of DNA strands

The asymmetric shape and linkage of nucleotides means that a DNA strand always has a discernible orientation or directionality. Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand (the "ascending strand"), and the other way along the other strand (the "descending strand"). This arrangement of the strands is called antiparallel.

Chemical nomenclature (5' and 3')

For reasons of chemical nomenclature, people who work with DNA refer to the asymmetric ends of each strand as the 5' and 3' ends (pronounced "five prime" and "three prime"). DNA workers and enzymes alike always read nucleotide sequences in the "5' to 3' direction". In a vertically oriented double helix, the 3' strand is said to be ascending while the 5' strand is said to be descending. In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ...

Sense and antisense

As a result of their antiparallel arrangement and the sequence-reading preferences of enzymes, even if both strands carried identical instead of complementary sequences, cells could properly translate only one of them. The other strand a cell can only read backwards. Molecular biologists call a sequence "sense" if it is translated or translatable, and they call its complement "antisense". It follows then, somewhat paradoxically, that the template for transcription is the antisense strand. The resulting transcript is an RNA replica of the sense strand and is itself sense. Molecular biology is the study of biology at a molecular level. ...

An exception: viruses

Some viruses blur the distinction between sense and antisense, because certain sequences of their genomes do double duty, encoding one protein when read 5' to 3' along one strand, and a second protein when read in the opposite direction along the other strand. As a result, the genomes of these viruses are unusually compact for the number of genes they contain, which biologists view as an adaptation. 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 biological adaptation is an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection such that it increases the expected long-term reproductive success of the organism. ...

As viewed by topologists

Topologists like to note that the juxtaposition of the 3' end of one DNA strand beside the 5' end of the other at both ends of a double-helical segment makes the arrangement a "crab canon". In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... In molecular biology, the 5 end and the 3 end (pronounced 5-prime and 3-prime) are respectively the leading and tail ends of a strand of nucleic acid. ... A crab canon is an arrangement of two things that are complementary and backward. ...

Single-stranded DNA (ssDNA) and repair of mutations

In some viruses DNA appears in a non-helical, single-stranded form. Because many of the DNA repair mechanisms of cells work only on paired bases, viruses that carry single-stranded DNA genomes mutate more frequently than they would otherwise. As a result, such species may adapt more rapidly to avoid extinction. The result would not be so favorable in more complicated and more slowly replicating organisms, however, which may explain why only viruses carry single-stranded DNA. These viruses presumably also benefit from the lower cost of replicating one strand versus two. Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). ... DNA damage resulting in multiple broken chromosomes DNA repair is a process constantly operating in each cell of a living being; it is essential to survival because it protects the genome from damage. ... 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 article is about mutation in biology, for other meanings see: mutation (disambiguation). ...

The history of DNA research

James Watson in the Cavendish Laboratory at the University of Cambridge

The discovery that DNA was the carrier of genetic information was a process which required many earlier discoveries. The existence of DNA was discovered in the mid 19th century. However, it was only in the early 20th century that researchers began suggesting that it might store genetic information. This was only accepted after the structure of DNA was elucidated by Watson and Crick, which they published in 1953. Watson and Crick proposed the central dogma of molecular biology in 1957, describing the process whereby proteins are produced from nucleic DNA. From http://wwwihm. ... From http://wwwihm. ... There is more than one person with the name James Watson: James Watson, author of the novel Talking in Whispers James Watson, U.S. Senator from New York (1797-1801) James Watson, painter of 77 portraits held by the U.S. National Portrait Gallery [[1]] James Watson, British radical, Chartist... The Cavendish Laboratory is in the Department of Physics of the University of Cambridge. ... The University of Cambridge is the second-oldest university in the English-speaking world. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... 1953 is a common year starting on Thursday. ... The central dogma of molecular biology (sometimes Cricks central dogma after Francis Crick who coined the term and discovered some of the principles) states that the flow of genetic information is DNA to RNA to protein. With a few notable exceptions, all biological cells conform to this rule. ... 1957 was a common year starting on Tuesday (link will take you to calendar). ... In cell biology, the nucleus (from Latin nucleus or nuculeus, kernel) is an organelle, found in all eukaryotic cells, which contains most of the cells genetic material. ...

First isolation of DNA

Working in the 19th century, biochemists initially isolated DNA and RNA (mixed together) from cell nuclei. They were relatively quick to appreciate the polymeric nature of their "nucleic acid" isolates, but realized only later that nucleotides were of two types--one containing ribose and the other deoxyribose. It was this subsequent discovery that led to the identification and naming of DNA as a substance distinct from RNA. Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... Ribose Ribose is a five carbon sugar (pentose) that is critical to living creatures. ... Deoxyribose Deoxyribose (more precisely 2-deoxyribose) is a five-carbon sugar (a pentose) derived from the pentose sugar ribose by the repacement of the hydroxyl group at the 2 position with hydrogen, leading to the net loss of an oxygen. ...

Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Somewhat later, he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes. Categories: Biology stubs | 1844 births | 1895 deaths ... 1844 was a leap year starting on Monday (see link for calendar). ... 1895 was a common year starting on Tuesday (see link for calendar). ... 1869 is a common year starting on Friday (link will take you to calendar). ... 1889 was a common year starting on Tuesday (see link for calendar). ...

Establishing a link between heritable traits and chromosomes

Max Delbrück, Nikolai V. Timofeeff-Ressovsky, and Karl G. Zimmer published results in 1935 suggesting that chromosomes are very large molecules the structure of which can be changed by treatment with X-rays, and that by so changing their structure it was possible to change the heritable characteristics governed by those chromosomes. (Delbrück and Salvador Luria were awarded the Nobel Prize in 1969 for their work on the genetic structure of viruses.) In 1943, Oswald Theodore Avery discovered that traits proper to the "smooth" form of the Pneumococcus could be transferred to the "rough" form of the same bacteria merely by making the killed "smooth" (S) form available to the live "rough" (R) form. Quite unexpectedly, the living R Pneumococcus bacteria were transformed into a new strain of the S form, and the transferred S characteristics turned out to be heritable. Avery called the medium of transfer of traits the transforming principle; he identified DNA as the transforming principle, and not protein as previously thought. In 1953, Alfred Hershey and Martha Chase did an experiment (Hershey-Chase experiment) that showed, in T2 phage, that DNA is the genetic material (Hershey shared the Nobel prize with Luria). Max Delbrück ( September 4, 1906 - March 9, 1981) was a German biologist. ... Nikolay Vladimirovich Timofeeff-Ressovsky (cyrillic here; September 7, 1900 - March 28, 1981) was a Russian biologist. ... Karl Gunter Zimmer ( 1911 - 1988) was a German scientist. ... 1935 was a common year starting on Tuesday (link will take you to calendar). ... 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... Salvador Edward Luria (August 13, 1912 - February 6, 1991) was a naturalized American microbiologist whose pioneering work on phage helped open up molecular biology. ... Photographs of Nobel Prize Medals. ... 1969 was a common year starting on Wednesday (the link is to a full 1969 calendar). ... 1943 is a common year starting on Friday. ... Oswald Avery in 1937 Oswald Theodore Avery ( 1877- 1955) was a physician, medical researcher and early molecular biologist. ... Griffiths experiment was conducted in 1928 by Frederick Griffith which was one of the first experiments suggesting that bacteria are capable of transferring genetic information, otherwise known as the “transforming principle”, which was later discovered to be DNA. Griffith used two strains of Pneumococcus (which infects mice), a S... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Alfred Day Hershey (December 4, 1908_1997) was a Nobel Prize-winning bacteriologist. ... Martha Chase was one of the leading researchers at the coveted Cold Spring Harbor Laboratory in the 1950s. ... The Hershey-Chase experiment was a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that identified DNA to be the genetic material of phages and, ultimately, of all organisms. ... Enterobacteria phage T2 is a virulent bacteriophage of the T4-like viruses genus, in the family Myoviridae. ... Genetic material is the material used to store genetic information for a living organism. ...

Francis Crick's first sketch of the deoxyribonucleic acid double-helix pattern

In 1944, the renowned physicist, Erwin Schrödinger, published a brief book entitled What is Life?, where he maintained that chromosomes contained what he called the "hereditary code-script" of life. He added: "But the term code-script is, of course, too narrow. The chromosome structures are at the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power -- or, to use another simile, they are architect's plan and builder's craft -- in one." He conceived of these dual functional elements as being woven into the molecular structure of chromosomes. By understanding the exact molecular structure of the chromosomes one could hope to understand both the "architect's plan" and also how that plan was carried out through the "builder's craft." Francis Crick, James D. Watson, Maurice Wilkins, Rosalind Franklin, Seymour Benzer, et al., took up the physicist's challenge to work out the structure of the chromosomes and the question of how the segments of the chromosomes that were conceived to relate to specific traits could possibly do their jobs. Francis Cricks first sketch of the deoxyribonucleic acid double-helix See also Image:Early sketch of DNA by Crick. ... Francis Cricks first sketch of the deoxyribonucleic acid double-helix See also Image:Early sketch of DNA by Crick. ... Photomontage of Francis Crick lecturing Francis Harry Compton Crick, OM (June 8, 1916 – July 28, 2004) was one of the discoverers of the structure of the DNA molecule. ... DNA replication Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. ... 1944 was a leap year starting on Saturday (link will take you to calendar). ... Erwin Schrödinger, as depicted on the former Austrian 1000 Schilling bank note. ... Photomontage of Francis Crick lecturing Francis Harry Compton Crick, OM (June 8, 1916 – July 28, 2004) was one of the discoverers of the structure of the DNA molecule. ... James Watson James Dewey Watson (born April 6, 1928) is one of the discoverers of the structure of the DNA molecule. ... Maurice Hugh Frederick Wilkins (December 15, 1916 – October 5, 2004) was a New Zealand born British physicist and Nobel Laureate who contributed research in the fields of phosphorescence, radar, isotope separation, and X-ray diffraction. ... Rosalind Franklin Rosalind Elsie Franklin (July 25, 1920 - April 16, 1958) was a British physical chemist and crystallographer who made important contributions to the understanding of the fine structures of coal, DNA and viruses. ... Categories: Wikipedia cleanup | Stub ...

Just how the presence of specific features in the molecular structure of chromosomes could produce traits and behaviors in living organisms was unimaginable at the time. Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform. Organisms, on the other hand, are fantastically complex individually and widely diverse collectively. Geneticists did not speak of genes as conveyors of "information" in such words, but if they had, they would not have hesitated to quantify the amount of information that genes need to convey as vast. The idea that information might reside in a chemical in the same way that it exists in text--as a finite alphabet of letters arranged in a sequence of unlimited length--had not yet been conceived. It would emerge upon the discovery of DNA's structure, but few researchers imagined that DNA's structure had much to say about genetics.

Crick and Watson DNA model built in 1953, currently on display at the National Science Museum in London.

Download high resolution version (960x1280, 178 KB) DNA model built by Crick and Watson in 1953. ... Download high resolution version (960x1280, 178 KB) DNA model built by Crick and Watson in 1953. ... Science Museum The Science Museum on Exhibition Road, Kensington, London, is part of the National Museum of Science and Industry. ...

Discovery of the structure of DNA

In the 1950s, only a few groups made it their goal to determine the structure of DNA. These included an American group led by Linus Pauling, and two groups in Britain. At the University of Cambridge, Crick and Watson were building physical models using metal rods and balls, in which they incorporated the known chemical structures of the nucleotides, as well as the known position of the linkages joining one nucleotide to the next along the polymer. At King's College, London, Maurice Wilkins and Rosalind Franklin were examining X-ray diffraction patterns of DNA fibers. Millennia: 1st millennium - 2nd millennium - 3rd millennium Events and trends Technology United States tests the first fusion bomb. ... Pauling lectured at Osaka University in 1955. ... The University of Cambridge is the second-oldest university in the English-speaking world. ... Kings College London (often abbreviated to KCL) in London is one of the largest colleges in the federal University of London, with 19,500 registered students. ... Maurice Hugh Frederick Wilkins (December 15, 1916 – October 5, 2004) was a New Zealand born British physicist and Nobel Laureate who contributed research in the fields of phosphorescence, radar, isotope separation, and X-ray diffraction. ... Rosalind Franklin Rosalind Elsie Franklin (July 25, 1920 - April 16, 1958) was a British physical chemist and crystallographer who made important contributions to the understanding of the fine structures of coal, DNA and viruses. ... Crystallography (from the Greek words crystallon = solid and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ...

Discovery that DNA is helical

A key inspiration in the work of all of these teams was the discovery in 1948 by Pauling that many proteins included helical (see alpha helix) shapes. Pauling had deduced this structure from X-ray patterns. Even in the initial crude diffraction data from DNA, it was evident that the structure involved helices. But this insight was only a beginning. There remained the questions of how many strands came together, whether this number was the same for every helix, whether the bases pointed toward the helical axis or away, and ultimately what were the explicit angles and coordinates of all the bonds and atoms. Such questions motivated the modeling efforts of Watson and Crick. 1948 is a leap year starting on Thursday (link will take you to calendar). ... A diagram of the alpha helix structure of amino acids In proteins, the α helix is a major structural motif in secondary structure. ...

Discovery that complementary nucleotides occur in equal proportions

In their modeling, Watson and Crick restricted themselves to what they saw as chemically and biologically reasonable. Still, the breadth of possibilities was very wide. A breakthrough occurred in 1952, when Erwin Chargaff visited Cambridge and inspired Crick with a description of experiments Chargaff had published in 1947. Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides -- adenine and thymine, guanine and cytosine -- the two nucleotides are always present in equal proportions. 1952 - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Erwin Chargaff (August 11, 1905 – June 20, 2002) was an Austrian biochemist. ... 1947 was a common year starting on Wednesday (link will take you to calendar). ...

Watson and Crick's model

Watson and Crick had begun to contemplate double helical arrangements, and they saw that by reversing the directionality of one strand with respect to the other, they could provide an explanation for Chargaff's puzzling finding. This explanation was the complementary pairing of the bases, which also had the effect of ensuring that the distance between the phosphate chains did not vary along a sequence. Watson and Crick were able to discern that this distance was constant and to measure its exact value of 2 nanometres from an X-ray pattern obtained by Franklin. The same pattern also gave them the 3.4 nanometre-per-10 bp "pitch" of the helix. The pair quickly converged upon a model, which they announced before Franklin herself published any of her work. Pitch may refer to: Pitch is the property of a sound or musical tone measured by its perceived frequency Pitch, or tone of voice, refers to variation of tone in tonal language, and in languages with melodic accent Pitch, a throw of a baseball by a pitcher Pitch, part of...

The chemical structure of DNA

The great assistance Watson and Crick derived from Franklin's data has become a subject of controversy, and it has angered people who believe Franklin has not received the credit due to her. The most controversial aspect is that Franklin's critical X-ray pattern was shown to Watson and Crick without Franklin's knowledge or permission. Wilkins showed it to them at his lab while Franklin was away. Download high resolution version (2048x1969, 97 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (2048x1969, 97 KB) Wikipedia does not have an article with this exact name. ...

Publishing of the "Central Dogma"

Watson and Crick's model attracted great interest immediately upon its presentation. Arriving at their conclusion on February 21, 1953, Watson and Crick made their first announcement on February 28. Their paper 'A Structure for Deoxyribose Nucleic Acid' (http://www.nature.com/genomics/human/watson-crick/) was published on April 25. In an influential presentation in 1957, Crick laid out the "Central Dogma", which foretold the relationship between DNA, RNA, and proteins, and articulated the "sequence hypothesis." A critical confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 in the form of the Meselson-Stahl experiment. Work by Crick and coworkers deciphered the genetic code not long afterward. These findings represent the birth of molecular biology. February 21 is the 52nd day of the year in the Gregorian Calendar. ... 1953 is a common year starting on Thursday. ... February 28 is the 59th day of the year in the Gregorian calendar. ... April 25 is the 115th day of the year in the Gregorian Calendar (116th in leap years). ... 1957 was a common year starting on Tuesday (link will take you to calendar). ... The central dogma of molecular biology (sometimes Cricks central dogma after Francis Crick who coined the term and discovered some of the principles) states that the flow of genetic information is DNA to RNA to protein. With a few notable exceptions, all biological cells conform to this rule. ... 1958 was a common year starting on Wednesday (link will take you to calendar). ... The Meselson-Stahl experiment was an experiment by Matthew Meselson and Franklin Stahl to prove that DNA replication was semiconservative. ... RNA codons. ... Molecular biology is the study of biology at a molecular level. ...

Watson, Crick, and Wilkins were awarded the 1962 Nobel Prize for Medicine for discovering the molecular structure of DNA, by which time Franklin had died. Nobel prizes are not awarded posthumously. James Watson James Dewey Watson (born April 6, 1928) is one of the discoverers of the structure of the DNA molecule. ... Photomontage of Francis Crick lecturing Francis Harry Compton Crick, OM (June 8, 1916 – July 28, 2004) was one of the discoverers of the structure of the DNA molecule. ... Maurice Hugh Frederick Wilkins (December 15, 1916 – October 5, 2004) was a New Zealand born British physicist and Nobel Laureate who contributed research in the fields of phosphorescence, radar, isotope separation, and X-ray diffraction. ... 1962 was a common year starting on Monday (link will take you to calendar). ... List of Nobel Prize laureates in Physiology or Medicine from 1901 to the present day. ... Rosalind Franklin Rosalind Elsie Franklin (July 25, 1920 - April 16, 1958) was a British physical chemist and crystallographer who made important contributions to the understanding of the fine structures of coal, DNA and viruses. ...

Bibliography

• DNA: The Secret of Life, by James D. Watson. ISBN 0-375-41546-7

External links

• DNA: PDB molecule of the month (http://nist.rcsb.org/pdb/molecules/pdb23_1.html)
• Open Directory Project: Nucleic Acids (http://www.dmoz.org/Science/Biology/Biochemistry_and_Molecular_Biology/Biomolecules/Nucleic_Acids/)
• 17 April, 2003, BBC News: Most ancient DNA ever? (http://news.bbc.co.uk/1/hi/sci/tech/2949629.stm)
• Watson, James, and Francis Crick, "Molecular structure of nucleic acids (http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html), A structure for Deoxyribose Nucleic Acid". April 2, 1953. (paper on the structure of DNA)
• My First Book About DNA (http://www.myfirstbookaboutdna.com) Designed for children to learn more about DNA.
• DNA Interactive (http://www.dnai.org) (requires Macromedia Flash)
• DNA under electron microscope (http://www.fidelitysystems.com/Unlinked_DNA.html)