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Chapter 2 Nucleic Acid Chemistry

Chapter 2 Nucleic Acid Chemistry. Composation Structure Function DNA RNA. 论述题 （课后查资料学习完成）. 论 述 DNA 双螺旋结构的特点及其生物学功能。 论述核酸分子杂交技术原理及其应用。. Nucleic acid is a heredity substace . 1928 年生理学家格里菲斯（ Griffith,J. ），在研究肺炎球菌时发现一种转化因子能够使无毒的 R 型细菌转变为有毒的 S 型双球菌。

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Chapter 2 Nucleic Acid Chemistry

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  1. Chapter 2 Nucleic Acid Chemistry Composation Structure Function DNA RNA

  2. 论述题 （课后查资料学习完成） • 论述DNA双螺旋结构的特点及其生物学功能。 • 论述核酸分子杂交技术原理及其应用。

  3. Nucleic acid is a heredity substace. • 1928年生理学家格里菲斯（Griffith,J.），在研究肺炎球菌时发现一种转化因子能够使无毒的R型细菌转变为有毒的S型双球菌。 • 1944，Oswald T. Avery（O.T.艾弗里，美国细菌学家）、Colin M. Macleod和Maclyn McCarty完成了肺炎双球菌体外转化实验，揭示了不同品系的肺炎双球菌相互之间的转化因子是DNA而不是蛋白质这一事实，首次证明DNA分子是遗传信息的载体。 • 1952，美国噬菌体学家Hershey A.D.（A.D.赫尔希）和Chase M.（M.蔡斯）用标记噬菌体感染实验研究证明，噬菌体 DNA携带着噬菌体复制的全部信息，再次证明了 DNA是遗传信息的载体，而不是蛋白质。

  4. Nucleic acid is a polymer of nucleotide,having and transfering genetic information, include deoxyribonucleic acid (DNA)and ribonucleic acid(RNA).

  5. Section 1 composition of nucleic acid

  6. Ribonucleoside核苷 The linkage of base with ribose(2-deoxyribose) by glycoside formed ribonucleoside(deoxynucleoside脱氧核苷). 核苷：腺苷AR,鸟苷GR,胞苷CR,尿苷UR。 脱氧核苷：脱氧腺苷dAR,脱氧鸟苷dGR,脱氧胞苷dCR,脱氧胸苷dTR。 cytidine胞苷CR guanine deoxyriboside 脱氧鸟苷dGR

  7. Nucleotide核苷酸 The product of ribonucleoside linking of phosphoric acid at 5’ position. 核苷酸： 腺苷酸AMP,鸟苷酸GMP,胞苷酸CMP,尿苷酸UMP。 脱氧核苷酸： 脱氧腺苷酸dAMP,脱氧鸟苷酸dGMP,脱氧胞苷酸dCMP,脱氧胸苷酸dTMP。 胞苷酸CMP 脱氧鸟苷酸dGMP

  8. Important nucleotide

  9. DNA was formed by linking of deoxynucleotides with phosphodiester bond at 3’ position of one deoxynucleotide and 5’ position of another deoxynucleotide. So is the RNA formation mode. The difference is at the nucleotide.

  10. 核酸一级结构思考题 1. 构成核酸的基本单位是什么？ 答：核苷酸。 2. 核苷酸通过什么键连接成高分子？ 答：3’,5’-磷酸二酯键。 3.DNA与RNA一级结构的主要区别有哪些？ 答：有两点： A.核糖不同。DNA，2－脱氧核糖；RNA，核糖。 B.碱基不同。DNA，ATGC；RNA，AUGC。

  11. Section 2 Dimensional structure and function of DNA • 1.Double-stranded helix • The two strands are antiparallel. • The chain, phosphoric acid and deoxyribose, locate lateral of the helix, but bases are in the helix. • Pair strictly A to T, G to C. • A turn contains 10 nucleotides, with height 3.4nm. • Width 2.0nm. • Form a major groove and a minor groove. • Rotating right-handed. • The maintaining force of the structure is hydrogen-bond and .

  12. bases pairs 2 hydrogen bonds 3 hydrogen bonds

  13. G/C含量越高，解开DNA双链将需要（更多，更少）的能量？G/C含量越高，解开DNA双链将需要（更多，更少）的能量？

  14. 2.0 nm 小沟 大沟 The Nobel Prize in Physiology or Medicine 1962 (1953) Watson and Crick

  15. Versatility of DNA double helix A型结构 碱基平面倾斜20º，螺旋变粗变短，螺距2～3nm。 Z型结构 左手螺旋，只有小沟

  16. 2.Tertiary structure of DNA----supercoil Further coil of the DNA double helix. 正超螺旋 负超螺旋

  17. 3. Nucleosome 核小体 DNA: ~200bp Histone: H1, H2A,H2B H3,H4.

  18. 4.Function of DNA Containing genetic information, as the template of gene duplication , DNA finally directs protein biosynthesis. As a result, keeping hereditary characters of body. Gene refer to a segment of DNA chain which posseses a special biological function.

  19. DNA高级结构思考题 • 1.DNA双螺旋B型结构是怎样的？ • 两条链反向平行 • 右手螺旋 • 核糖、磷酸构成的主链在外，碱基在内 • 碱基A-T,G-C配对 • 每10个核苷酸完成1个360°螺旋 • 螺距3.4nm • 宽度2.0nm • 形成1大沟和1小沟 • 结构的维持力是氢键与碱基堆积力 2.构成染色质的基本单位是什么？ 答：核小体 3.构成核小体核心颗粒的蛋白质有哪些？ 答：组蛋白H2A、H2B、H3及H4各两分子。 4.核小体DNA的长度是多少？ 答：约200bp。 5.原核生物DNA的立体结构是怎样的？ 答：一般为环状双螺旋。在一定条件下可形成超螺旋。

  20. Section3 spatial structure and function of RNA RNAs in animal cell

  21. mRNA --messenger RNA • 5’cap:m7GpppNm-，保护、促进与核蛋白体结合、加速翻译起始 • 3’Poly A tail：An n=20—200，与mRNA的转位与稳定性有关 • Single chain • half life time from munits to hours

  22. tRNA --transfer RNA • Stem-loop structure, cloverleaf pattern三叶草形. • 3 loop and 1 arm: DHU loop, anticoden loop, Tφloop, AA arm. • Anticoden and CCA-OH 3’end. • Contain rare bases 10%-20%.

  23. Rare bases Ψ I DHU mG Ψ：pseudouracil假尿嘧啶，I：hypoxanthine次黄嘌呤， DHU：dihydrouracil二氢尿嘧啶， mG：7-methylguanine7-甲基鸟嘌呤．

  24. tRNA tertiary structure: a inverse L like.

  25. tRNA functions as a amino acid transfer in protein biosynthesis.

  26. rRNA --ribosomal RNA • Weight 80% of total RNA in a cell. • Flower like. • Component of ribosome. • procaryote：5S,16S,23S; eukaryote: 18S,5S,5.8S,28S Eukaryote 18S rRNA

  27. RNA高级结构思考题 试比较mRNA、tRNA与rRNA在结构与功能上的异同

  28. Section 4. physical and chemical properties of nucleic acid • General character • acidity. • high viscosity of DNA • breaking easily

  29. 2. Ultraviolet absorption • Nucleic acids get their maximum absorption at 260nm. • DNA solution： A260／A280=1.8; RNA solution： A260／A280= 2.0 • OD260=1.0, equal to 50μg/ml DS DNA, 40μg/ml SS DNA or RNA.

  30. 3. DNA denaturation --the double chain change into single chain. Methods: heat, acid, base, urea, acetone Result: OD260↑, viscosity↓, activity lose.

  31. Tm --melting temperature, 解开链温度，融解温度，refer tothe middle point of temperature range of DNA thermal denaturation . • The temperature of 50% double chain undoing. • Tm=69.3+0.41(G+C)%

  32. 4.Renaturation and hybridization Renaturation: the single DNA chains recover their natural double helix structure. Annealing退火: renaturation of thermal denatural DNA, by way of slow cooling. Hybridization杂交：phenomenon of single chain DNA or RNA bind the chain different origin in renaturation process.

  33. Section 5. nucleases核酸酶 • Nuclease: hydrolysis of nucleic acid. • DNase: hydrolysis of DNA. • RNase: hydrolysis of RNA. • exonuclease外切酶： act at the end of the chain • endonuclease核酸内切酶：act at the inner part of the chain • restriction enzyme限制性内切酶：cut a special point of the chain. • ribozyme核酶：consists of RNA, not protein.

  34. 选择题练习

  35. 1. The element that could be used in nucleic acid quantitation is ( ) A. C B. O C. N D. H E. P

  36. 2. The basic unit composition of nucleic acid is ( ) A. Ribose and deoxyribose B. phosphoric acid and pentaglucose C. Pentaglucose and basic group D. mononucleotide E. phosphoric acid，pentose and basic group

  37. 3．脱氧核糖核苷酸彻底水解，生成的产物的产物是( ) A 核糖和磷酸 B 脱氧核糖和碱基 C 脱氧核糖和磷酸 D 磷酸，核糖和碱基 E 脱氧核糖，磷酸和碱基

  38. 4．在核酸分子中核苷酸之间的连接方式是( ) A. 3’,3’－磷酸二酯键 B. 糖苷键 C. 2’,5’ －磷酸二酯键 D. 肽键 E. 3’,5’－磷酸二酯键

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