脫氧核糖核酸

脫氧核醣核酸（粵拼：tyut3 joeng5 hat6 tong4 hat6 syun1），又叫 DNA（粵拼：di1 en1 ei1），係英文學名 deoxyribonucleic acid 嘅簡寫，同叫去氧核醣核酸，係一種分子，可以組成遺傳指令，用嚟引導生物發育同生命機能嘅運作，主要係長期性資訊儲存。裏面包含嘅指令，係建造細胞嘅化合物（例如蛋白質同RNA）用得着嘅。帶有遺傳訊息嘅DNA片段叫做基因。

1953年James D. Watson同埋Francis Crick發現DNA係雙螺旋構造。

物理同化學性質

脫氧核醣核酸係一種由核苷酸重複排列組成嘅長鏈聚合物^[1]^[2]，寬度約莫22到24埃（2.2到2.4納米），每一個核苷酸單位就大約長3.3埃（0.33納米）^[3]。喺成個脫氧核醣核酸聚合物入面，可能有幾百萬個連住嘅核苷酸。例如人類細胞入面最大嘅1號染色體入面，就有2億2千萬個鹼基對^[4]。通常喺生物體入面，脫氧核醣核酸唔係單一分子，而係形成兩條兩條配對同緊密結合^[5]^[6]，而且好似蔓藤咁纏繞做雙螺旋結構嘅分子。每個核苷酸分子嘅磷酸同脫氧核醣會互相連結，做成長鏈骨架；另一部分叫做鹼基，可以令一對嘅兩條脫氧核醣核酸互相結合。所謂核苷酸，係指一個核苷加一個或者多過一個磷酸基團，核苷就係指一個鹼基加一個糖類分子^[7]。

脫氧核醣核酸骨架是由磷酸同糖類基團交互排列整成^[8]。組成脫氧核醣核酸嘅糖類分子係環狀嘅2-脫氧核醣，屬於五碳糖嘅一種。磷酸基團上嘅兩個氧原子分別連喺五碳糖喺3號同5號碳原子上面，形成磷酸雙酯鍵。呢種兩邊唔對稱嘅共價鍵位，令條條脫氧核醣核酸長鏈都有方向性。雙螺旋入面嘅兩個核苷酸互相用相反方向排列，呢種排列方式叫做反平行。脫氧核醣核酸鏈上互相唔對稱嘅兩末端一邊叫做5'端，另一邊就叫做3'端。脫氧核醣核酸同RNA最主要嘅唔同之一，係响組成糖分子嘅不同，DNA係2-脫氧核醣，而RNA係核醣^[6]。

參考

↑ Alberts, Bruce (2002). Molecular Biology of the Cell; Fourth Edition. New York and London: Garland Science. ISBN 0-8153-3218-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
↑ Butler, John M. (2001) Forensic DNA Typing "Elsevier". pp. 14 – 15. ISBN 978-0-12-147951-0.
↑ Mandelkern M, Elias J, Eden D, Crothers D (1981). "The dimensions of DNA in solution". J Mol Biol. 152 (1): 153–61. PMID 7338906.{{cite journal}}: CS1 maint: multiple names: 作者名單 (link)
↑ Gregory S; 等 (2006). "The DNA sequence and biological annotation of human chromosome 1". Nature. 441 (7091): 315–21. PMID 16710414. {{cite journal}}: Explicit use of et al. in: |author= (help)
↑ Watson J, Crick F (1953). "Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid" (PDF). Nature. 171 (4356): 737–8. PMID 13054692.
↑ ^6.0 ^6.1 Berg J., Tymoczko J. and Stryer L. (2002) Biochemistry. W. H. Freeman and Company ISBN 0-7167-4955-6
↑ Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents IUPAC-IUB Commission on Biochemical Nomenclature (CBN) Accessed 03 Jan 2006
↑ Ghosh A, Bansal M (2003). "A glossary of DNA structures from A to Z". Acta Crystallogr D Biol Crystallogr. 59 (Pt 4): 620–6. PMID 12657780.

[Alberts-1] Alberts, Bruce (2002). Molecular Biology of the Cell; Fourth Edition. New York and London: Garland Science. ISBN 0-8153-3218-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[Butler-2] Butler, John M. (2001) Forensic DNA Typing "Elsevier". pp. 14 – 15. ISBN 978-0-12-147951-0.

[3] Mandelkern M, Elias J, Eden D, Crothers D (1981). "The dimensions of DNA in solution". J Mol Biol. 152 (1): 153–61. PMID 7338906.{{cite journal}}: CS1 maint: multiple names: 作者名單 (link)

[4] Gregory S; 等 (2006). "The DNA sequence and biological annotation of human chromosome 1". Nature. 441 (7091): 315–21. PMID 16710414. {{cite journal}}: Explicit use of et al. in: |author= (help)

[Watson-5] Watson J, Crick F (1953). "Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid" (PDF). Nature. 171 (4356): 737–8. PMID 13054692.

[berg-6] 6.0 ^6.1 Berg J., Tymoczko J. and Stryer L. (2002) Biochemistry. W. H. Freeman and Company ISBN 0-7167-4955-6

[IUPAC-7] Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents IUPAC-IUB Commission on Biochemical Nomenclature (CBN) Accessed 03 Jan 2006

[Ghosh-8] Ghosh A, Bansal M (2003). "A glossary of DNA structures from A to Z". Acta Crystallogr D Biol Crystallogr. 59 (Pt 4): 620–6. PMID 12657780.

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