Béda révisi "DNA"

1 bita dipupus ,  4 tahun yang lalu
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Ngarapihkeun éjahan, replaced: sahingga → antukna (3), model → modél (2) using AWB
m (Ngarapihkeun éjahan, replaced: ngarupakeun → mangrupa (3), salasahiji → salah sahiji, Kusabab → ku sabab (3) using AWB)
m (Ngarapihkeun éjahan, replaced: sahingga → antukna (3), model → modél (2) using AWB)
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—A ka T jeung C ka G -- sahinggaantukna 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.
 
ku 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.
[[Gambar:Dna-helix.png|frame|Modél ''ngeusi rohangan'' (''space-filling'') potongan molekul DNA]]
 
Beungkeut hidrogén antara lambaran héliks ganda cukup lemah sahinggaantukna 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.
 
== DNA ''single-stranded'' (ssDNA) jeung ngoméan mutasi ==
Dina saababaraha [[virus]], DNA téh aya dina bentuk lambar tunggal sarta nonhéliks. ku 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 sahinggaantukna teu lastari.
 
== Rujukan ==
* Watson, James, and Francis Crick, "''[http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html Molecular structure of nucleic acids], A structure for Deoxyribose Nucleic Acid''". April 2, 1953. (paper on the structure of DNA)
* [http://www.dnai.org DNA Interactive] (requires [[Macromedia Flash]])
* [http://www.indigo.com/models/dna-models.html DNA model] - sometimes a solid three-dimensional modelmodél, rather than an in silico modelmodél, is the best for demonstrating the structure of DNA (viz. Watson and Crick!)
 
[[Kategori:Asam nukléat]]