Béda révisi "DNA"

18 bita dipupus ,  4 tahun yang lalu
m
Ngarapihkeun éjahan, replaced: ngarupakeun → mangrupa (3), salasahiji → salah sahiji, Kusabab → ku sabab (3) using AWB
m (Ngarapihkeun éjahan, replaced: ngarupakeun → mangrupa (3), salasahiji → salah sahiji, Kusabab → ku sabab (3) using AWB)
[[Gambar:dna-split.png|frame|Réplikasi DNA]]
'''Asam déoksiribonukléat''' (''Deoxyribonucleic acid'', '''DNA''') ngarupakeunmangrupa [[asam nukléat]] nu mawa [[paréntah]] [[genetik]] pikeun [[biologi pertumbuhan|pertumbuhan biologis]] sadaya bentuk [[mahluk hirup|kahirupan]] jeung rupa-rupa [[virus]]. DNA kadang disebut salaku [[molekul]] [[warisan]] sabab [[warisan biologis|diwariskeun]] sarta digunakeun pikeun ngabaranahkeun [[sifat]]. Nalika [[réproduksi]], DNA [[Réplikasi DNA|disalin]] sarta diteruskeun ka turunan.
 
Dina [[baktéri]] jeung organisme [[sél biologis|sél]] [[prokariot|basajan]] séjénna, DNA nyebar kurang leuwih ampir di sapanjang jero sél. Na sél [[yukariot|kompléks]] nu nyusun ta[[tangkal]]an, [[sato]], sarta [[organisme]] multisél séjén, lolobana DNA kapanggih na [[kromosom]] nu aya na [[inti sél]]. [[Organél]] nu ngahasilkeun énergi nu katelah salaku [[kloroplas]] jeung [[mitokondria]] ogé mawa DNA, nya kitu ogé rupa-rupa [[virus]].
== Ihtisar struktur molekular ==
 
Najan kadang disebut "molekul warisan", lambaran DNA teu mangrupa molekul tunggal. DNA mangrupa pasangan molekul, nu murilit kawas tambang nu ngawujud jadi hiji '''[[héliks]] ganda''' (bagéan luhur na gambar katuhu).
 
Unggal lambar molekul ngarupakeunmangrupa salambar DNA: hiji ranté [[nukléotida]] nu numbu kimiawi nu masing-masing ngandung hiji [[gula]], hiji [[fosfat]], jeung salasahijisalah sahiji ti opat "[[basa nirogénan|basa]]" [[hidrokarbon aromatik|aromatik]]. Kusababku sabab lambaran DNA diwangun ku subunit-subunit nukléotida ieu, mangga kaasup [[polimér]].
 
Kabinékaan basa ieu ngandung harti yén aya opat rupa nukléotida, nu biasa ditujul dumasar basana, nyaéta [[adénin]] (A), [[timin]] (T), [[sitosin]] (C), jeung [[guanin]] (G).
 
Dina héliks ganda, dua lambar polinukléotida ngahiji dina [[pasangan basa|papasangan kompleméntér]] basa-basana ku ayana [[beungkeut hidrogén]]. Unggal basa nyieun beungkeut hidrogén ukur jeung pasangan nu tinangtu -- Atinangtu—A ka T jeung C ka G -- sahingga idéntitas basa na hiji lambar nangtukeun basa naon nu aya na lambar lawanna. Sakujur [[struktur primér|wangun]] nukléotida dina unggal lambar téh kompleméntér jeung pasanganana. Mun dipisahkeun, unggal lambar éta bisa dijadikeun citakan pikeun [[réplikasi|nyieun]] pasanganana.
 
Kusababku sabab papasangan basa nukléotidana aya dina sumbu héliks, mangka gugus gula jeung fosfatna ngaruntuy di bagian luar. Ranté anu dibentuk ku pasangan ieu gula-fosfat sok disebut "tulang tonggong" (''backbones'') héliks.
 
== Pentingna runtuyan ==
 
Dina hiji gén, runtuyan nukléotida sapanjang lambar DNA nangtukeun hiji [[protéin]], nu perlu dijieun ku hiji [[organisme]] atawa "[[éksprési gén|diéksprésikeun]]" sakali atawa sababaraha kali nalika hirupna migunakeun béja runtuyanana. Hubungan antara runtuyan nukléotida jeung runtuyan [[asam amino]] protéinna ditangtukeun ku aturan [[Tarjamah (biologi)|tarjamah]] sélular basajan, nu sacara koléktif katelah salaku [[sandi genetik]]. Maca sapanjang runtuyan "panyandi protéin" hiji gén, unggal tilu runtuy nukléotida (disebut [[kodon]]) nangtukeun atawa "nyandi" hiji asam amino.
 
Di loba [[spésiés]], jigana ukur sabagéan leutik tina sakabéh runtuyan [[génom]] nu nyandi protéin. Fungsi nu sésana nepi ka kiwari can dipikanyaho. Geus dipikanyaho yén aya runtuyan nukléotida nu nangtukeun ''affinity'' pikeun [[protéin pamengkeut DNA]] (''DNA binding protein'') nu boga rupa-rupa peran penting, hususna dina ngatur réplikasi jeung transkripsi. Runtuyan ieu mindengna disebut [[runtuyan pangatur]] (''regulatory sequence''), bari panalungtik nganggap yén sajauh ieu mah aranjeunna bisa manggihan ngan saeutik ti antarana. "[[DNA runtah]]" (''junk DNA'') nunjukkeun runtuyan nu can kapanggih mibanda gén atawa fungsi.
..[[origin of replication]]...chromosome...plasmid...DNA polymerase...[[mutation]]...[a paragraph including these ideas would be useful and go well here]
-->
Réplikasi DNA atawa sintésis DNA ngarupakeunmangrupa prosés nyalin DNA lambar-ganda nuturkeun ayana ''[[pembelahan sél]]''. Lambaran ganda nu dihasilkeun sacara umum ampir sarua samasakali, ngan kasalahan dina réplikasi bisa ngakibatkeun salinan nu teu sampurna (tempo [[mutasi]]). Unggal lambar ganda nu dihasilkeun ngandung salambar nu asli sarta salambar nu anyar disintésis. Ieu disebutna ''[[réplikasi semikonservatif]]''. Prosés réplikasi ngawengku tilu hambalan: ''inisiasi'', ''réplikasi'', jeung ''terminasi''.
 
== Sifat mékanis nu patali jeung biologi ==
[[Gambar:Dna-helix.png|frame|Modél ''ngeusi rohangan'' (''space-filling'') potongan molekul DNA]]
 
Beungkeut hidrogén antara lambaran héliks ganda cukup lemah sahingga bisa leupas kalawan gampang ku ayana [[énzim]]. Énzim nu katelah [[hélikase]] ngudar lambaran pikeun ngajalanan majuna énzim nu maca runtuyan kayaning [[polimérase DNA]]. <!--The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The stands 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.
 
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 [[knot theory|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 [[topoisomerase]]s. 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.
 
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 [[nanometer]]s wide and extends 3.4 nanometers per 10 bp of sequence. This is also the approximate length of sequence in which the 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.
 
The narrow breadth of the double helix makes it impossible to detect by conventional [[transmission electron microscope|electron microscopy]], except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length -- approximately 5 [[centimetre|centimeters]] 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 [[protein]]s known as [[histone]]s, around which DNA winds.
 
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 "[[supercoil|supercoiled]]". DNA <i>in vivo</i> is typically negatively supercoiled, which facilitates the unwinding of the double-helix required for [[transcription|RNA transcription]].
 
== Maca runtuyan DNA ==
Bentuk jeung beungkeut nu asimétri dina nukléotida ngandung harti yén salambar DNA salawasna mibanda ''a discernable orientation'' atawa ''directionality''. Ku sabab kitu, najan salambar nukléotida nujul ka hiji "arah", nu séjénna (pasanganana) pasti nujul ka sabalikna. Susunan lambar kieu disebutna '''antiparalél'''.
 
Pikeun alesan tata ngaran kimia, urang kudu ngarujuk ka tungtung asimétri dina unggal lambaran DNA-na salaku tungtung '''5'''' jeung '''3'''' (dibaca "prima lima" jeung "prima tilu"). Olah DNA (misalna nu ngalibetkeun [[énzim]]) ilaharna maca runtuyan nukléotida ti "'''5' ka 3''''". Dina ilustrasi héliks ganda nu nangtung/vértikal, lambaran 3' biasana naék, sedengkeun lambaran 5' sabalikna.
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 biology|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.''
 
Some viruses blur the distinction between sense and antisense, because certain sequences of their [[genome|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]].
 
Topologists like to note that the juxtaposition of the 3' end of one DNA strand beside the 5' end of the other at both termini of a double-helical segment makes the arrangement a "[[crab canon]]".-->
 
== DNA ''single-stranded'' (ssDNA) jeung ngoméan mutasi ==
Dina saababaraha [[virus]], DNA téh aya dina bentuk lambar tunggal sarta nonhéliks. Kusababku sabab mékanisme [[ngoméan DNA]] mah biasana lumangsung dina basa-basa nu papasangan, virus nu ngan boga [[génom]] ssDNA [[mutasi]]na leuwih mindeng batan mun boga utas ganda. Balukarna, aya spésiés-spésiés nu bisa adaptasi leuwih gancang sahingga teu lastari.
 
== Rujukan ==
[[Kategori:Asam nukléat]]
[[Kategori:Génétika]]
[[kategoriKategori: Biotéhnologi]]
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