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'''Deoxyribonucleic acid''' (DNA) is an a chemical inside [[organic compound|organiccell]] s which carries the hereditary information. It is a molecular [[chemical compoundpolymer]] made up formed of [[moleculenucleotide|deoxyribonucleotides]]s shaped like a . All organisms use DNA as their hereditary material. [[double helixOffspring]], a continuously twisted ladder. The individual monomeric building blocks of DNA (and other nucleic acids) are [[nucleotidesHuman reproduction|Sexual reproduction]], which themselves consist of three principle moieties: A nitrogenous base, a sugar, and a phosphate group[[organisms|Organism]] contain DNA from both parents.
DNA carries the [[gene|genet]]ic coding for the [[protein]]s that form the bodies of living [[organism]]s. All organisms contain DNA, and the DNA of a sexually reproducing organism is a mix of its parents' DNA.==Structure==
==History==In the late 19th century Most commonly as a double-stranded [[Friedrich Miescherhelix]]comprising two complimentary molecules held together by hydrogen bonds, a Swiss this is commonly called "dsDNA" (double-stranded DNA).<ref>Single-stranded DNAs (ssDNA) do exist in certain [[biochemistbacteriophage]]s, discovered several different proteins and an unusual [[acid]] in however they cannot be replicated without first creating the [[nucleus]] of cellscomplimentary strand to use as a template. </ref> The acid was named deoxyribonucleic acid, or DNA. In 1944 two American [[biologistnucleotide]]swhich are the "building blocks" of DNA have three main parts: A nitrogenous base (the "letters" in the sequence), a [[Alfred Hersheysugar]] , and a [[Martha Chasephosphate]] used experiments group. When nucleotides are joined into DNA strands, they form a chain with [[bacteria]] and [[bacteriophages]] to show that DNA passed [[gene]]s from the phosphate group of one generation nucleotide binding to the ribose of the next.
At that timeDNA strands "compliment" each other by having compatible sequences, it was unclear how this simple molecule could hold all allowing the complex information controlling bases on one strand to form bonds with the development of humans, animals and plantsbases on the other strand. Scientists knew it was made of There are four chemical nitrogenous bases called [[adenine]] , Adenonine (A), [[thymine]] Cytosine (TC), [[guanine]] Guanine (G) , and [[cytosine]] Thymine (CT), plus [[phosphoric acid]] and a [[sugar]]. They also knew that there was always Under the same amount of base pairing rules, A as pairs with T and of G as pairs with C in cells, but they did not know the rules that controlled the arrangement.
British scientists DNA contains [[Rosalind Franklingene]] and s that encode for [[Maurice Wilkinsprotein]] passed [[X-ray|X-rays]] through DNA to study s. These are produced by the patterns made when the crystals diffracted them. From studying photographs of patterns, Rosalind Franklin concluded that DNA must be be a first being turned into m[[helix]]. [[James WatsonRNA]] and then into polypeptides (this process is called the [[Francis CrickCentral dogma of molecular biology|central dogma]], working in [[Cambridge]], used this information to help them solve the puzzle of DNA structuremolecular biology). They built a model showing that if A always paired with T and G paired with C, All organisms use DNA must be like a ladder made of two strands twisted together in a double helixas their hereditary material. The sugar and phosphoric acid were the sides Offspring of the ladder, and the rungs were the paired basessexually reproducing organisms contain DNA from both parents.
Watson and Crick suggested that DNA could unzip itself into two separate strands==History==In the late 19th century [[Friedrich Miescher]], and each strand could act as a pattern to grow a new strand. Crick showed later that each pair of genes worked Swiss [[biochemist]], discovered an unusual [[acid]] in a group of three making the code for amino acids, the building blocks [[nuclei]] of proteinscells. These groups are called The acid was named deoxyribonucleic acid, or DNA. In 1944 the American [[codon|codonsbiologist]]. They make about fifty thousand different types of s, [[proteinAlfred Hershey]], which make all the different types of cell in the body. Indian biochemist [[Har Gobind KhoranaThomas Gilmore]] made all the possible codons and worked out which codons controlled which [[amino acidMartha Chase]]used experiments with [[bacteria]] and [[bacteriophage]]s to show that DNA passed [[gene]]s from one generation to the next.
If the DNA in one cell was stretched outAt that time, it would be about three feet long. Although DNA has a very was unclear how this simple structuremolecule could hold all the complex information controlling the development of humans, animals and plants. Scientists knew it can carry an enormous amount was made of four chemical bases called [[informationadenine]]. Scientists do not yet understand all the DNA they see(A), but in 1991 a project called the [[Human Genome Projectthymine]] began to use computers to map the three billion base pairs which make up the 46 human (T), [[chromosome|chromosomesguanine]](G) and [[cytosine]] (C), plus [[phosphoric acid]] and a [[sugar]]. They also knew that the ratios of A and T as well as G and C were always the same, but they did not know the rules that controlled the arrangement.
==Modern understanding==British scientists [[Image:818.gif|right|thumb|Structure of DNA.Rosalind Franklin]]Small parts of DNA called and [[geneMaurice Wilkins]]s serve as the instructions for the body to carry out its functions and give rise to traits such as eye color, hair color, etc. <ref>"Eye passed [[X-color genes, ray]]s through DNA to study the proteins they encode, direct patterns made when the amount and placement of melanin in the iriscrystals diffracted them." From studying photographs of patterns, Rosalind Franklin concluded that DNA must be a [http://www.hhmi[helix]].org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fgenetics%2Fans_044.html Ask A Scientist - Genes [[James Watson]] and eye color[[Francis Crick]</ref> Genes are packaged into ], working in [[chromosomesCambridge]]. Each individual human being has 23 pairs , used this information to help them solve the puzzle of chromosomesDNA structure. They built a model showing that if A always paired with T and G paired with C, where one set is inherited from his/her mother DNA must be like a ladder made of two strands twisted together in a double helix. The sugar and phosphoric acid were the other set is inherited from his/her father. 22 sides of these chromosomes are referred to as autosomesthe ladder, while and the remaining chromosome determines gender (sex chromosome)rungs were the paired bases that were held together through hydrogen bonding.
[[Prokaryotic Watson and Crick suggested that DNA]] is circular (could unzip itself into two separate strands, and each strand could act as a closed loop)pattern to grow a new strand. Crick showed later that areas of the DNA known as genes worked in groups of three to code for amino acids, while the building blocks of proteins. These groups are called [[Eukaryotic DNAcodon]] is linear (with ends) with the exception s. They make about fifty thousand different types of [[Mitochondrial DNAprotein]], which is circular too. DNA make all the different types of cell in the body. Indian biochemist [[prokaryoteHar Gobind Khorana]] made all the possible codons and worked out which codons controlled which [[amino acid]]s usually consists only of one closed loop chromosome.<ref>CampbellMost codons are redundant and code for the same amino acids, Neil A, et. althese mostly are different in only the third base pair. ''Biology''. 6th ed. San Francisco: Benjamin Cummings, 2002. 299, 530-31This means that differences in genotype can build up in the third position (thereby changing the genotype) without changing the protein (keeps the same phenotype).</ref>
If the DNA changes account for differences between individualsin one cell was stretched out, it would be about three feet long. HoweverAlthough DNA has a very simple structure, they it can also cause medical problems such as carry an enormous amount of [[cancerinformation]]. Scientists do not yet understand the function of all DNA, but in 1991 a project called the [[Human Genome Project]] began to use computers to map the three billion base pairs which make up the 46 human [[chromosome]]s.
DNA is ==Modern understanding==[[transcriptionImage:818.gif|transcribedright|thumb|Structure of DNA.]] into Small lengths of DNA called [[mRNAgene]]s serve as the instructions for the body to carry out its functions and give rise to the physical traits of the organism.<ref>"Eye-color genes, which is through the proteins they encode, direct the amount and placement of melanin in turn the iris." [[translation|translated]http://www.hhmi.org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fgenetics%2Fans_044.html Ask A Scientist - Genes and eye color] </ref> DNA is packaged into [[proteinschromosomes]] built from . Each individual human being has 23 pairs of [[amino acidschromosome]]. Additionallys, DNA maybe transcribed into functional RNAs (ribosomal where one set is inherited from his/her mother and transfer RNA) that do not undergo translationthe other set is inherited from his/her father. 22 of these chromosomes are referred to as [[RNAautosome]] can also be reverse-transcribed back into DNAs, which while the remaining chromosomes are the sex chromosomes. Males possess a single X chromosome and a single Y chromosome; whereas females possess a pair of X chromosomes. In total, it is estimated that there are roughly 20300 protein-coding genes in the called [[Complimentary DNA]] or [[cDNA]]human genome; however, due to mRNA splicing, it is estimated that these genes encode for over 1 million different protein products.
==[[Prokaryotic DNA fingerprinting==]] is circular (a closed loop). Whereas, [[eukaryotic DNA|eukaryotic chromosomes]] are linear (with ends), with the notable exception of [[Mitochondrial DNA]] and plastid (chloroplast) DNA, which is separate from the DNA in the nucleus.<ref>Mitochondria and chloroplasts are thought to have originated as prokaryotic cells living symbiotically inside of primitive eukaryotic cells, this is called the [[endosymbiotic hypothesis]]</ref> The ends of eukaryotic chromosomes are protected by [[telomere]]s, which are always tightly condensed except during S phase of [[mitosis]].<ref>Campbell, Neil A, et. al. ''Biology''. 6th ed. San Francisco: Benjamin Cummings, 2002. 299, 530-31.</ref>
[[Mutation]]s are simply variations in DNA can help police track down criminals if an attacker leaves something like hair or blood at a crime scenesequence between individuals. Everybody’s The vast majority of spontaneous mutations in DNA is unique unless they are identical twins, and called "neutral" because they do not affect the genetic ‘fingerprint’ [[phenotype|observable traits]] of this material the individual organism. Others can be enough to confirm if a suspect have beneficial effects and some can disrupt important functions Differential distribution of various types of neutral mutations within the population is guilty. Genetic the basis for modern [[DNA fingerprinting can also show if somebody ]]. It is closely related mutations in DNA, giving rise to somebody elsenovel alleles ("versions" of a gene), which cause phenotypic variations between individuals of a particular species. Archaeologists used samples from living relatives to identify whether bodies found buried For instance, in a forest humans, single-gene mutations are responsible for differences in [[RussiaABO blood type]] were , eye color, hair color, and even the remains ability to taste certain molecules. Sadly, there are also thousands of the [[Tsar]] mutations known to cause human disease; notably sickle-cell anemia, a few rare forms of autism, and his family(when the mutations spontaneously occur in a somatic cell) various types of cancer. That said, killed during it is important to note that most phenotypic traits (e.g. height) and hereditary diseases arise as the 1919 [[Russian revolution]]net effect of several different genetic variations.
As well as showing how different we all are, DNA shows how much we are all the same[http://www. Only one small part ncbi.nlm.nih.gov/omim OMIM] (Online Mendelian Inheritance in Man), is an online database of one chromosome distinguishes a boy from genes known to be mutated in disease states. [[Mendelian inheritance]] refers to the inheritance pattern observed in traits that are determined by a girlsingle gene. Genes give us different colored eyes This pattern was first discovered by [[Gregor Mendel]], hair and skinan Austrian monk, but 99during his work with pea plants from 1856-1863.5% of any human Although Mendel published his work in 1866, it's DNA is significance was largely ignored until it was rediscovered in the same order as everybody else’s, and 98.6% is the same as a chimpanzee’searly 20th century; more than two decades after his death.
Every living thing on earth has DNA that uses the same basic chemicals as human DNA, but because their chemicals are in a different order, the DNA of a worm or a tree encodes for different proteins, and those proteins make different cells. Evolutionists believe that all these cells developed from the first single-cell creatures formed three thousand million years ago, evolving gradually into new species to adapt to their environment. Creationists believe that God created all species the way they are now.
Whatever their individual beliefs, only human beings have learned to analyze and use their ==See also==*[[DNA, and only humans can learn to use that knowledge wisely.library]]*[[Transcription]]
==External links==
*[http://www.learner.org/interactives/dna/index.html Interactive DNA] Learn about genetics, genetic engineering, the Human Genome Project and the ethical implications of these new technologies.
*[http://www.blackwellpublishing.com/trun/artwork/Animations/cloningexp/cloningexp.html Animated guide to DNA cloning]
[[Category:Genetics]]
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