dna dan rna unit struktural dalam sel n.
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DNA dan RNA UNIT STRUKTURAL DALAM SEL

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DNA dan RNA UNIT STRUKTURAL DALAM SEL

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  1. DNA dan RNAUNIT STRUKTURAL DALAM SEL AgustinaSetiawati, M.Sc., Apt

  2. Albert, 1994, Molecular Biology of the Cell, Mc Graw Hill REFERENSI

  3. Nucleus Kromosomdalamsel Chromosome

  4. Kromosom tanpa histon

  5. Each cell has 46 chromosomes (in 23 pairs) • ~30,000 genes are arranged along the 23 types of chromosomes

  6. Genes come in homologous pairs • The location of a gene on a chromosome = locus. • Alternative forms of genes that influence a characteristic = alleles.

  7. A gene pair of two same alleles (i.e., AA) = homozygous • A gene pair of two different alleles (i.e., AO) = heterozygous. DNA Introduction, cont.

  8. Genotype: The particular combination of genes present in the cells of an individual (AA or AO) • Phenotype: The physical trait such as, shape, color, blood type, etc. DNA Introduction, cont.

  9. Human 4 x 109  22 autosom yang berbeda 2 sex kromosom Masing2 single linier DNA E. Coli 4.7 x 106 1 Chromosom 40 – 50 loop superkoil

  10. Merupakan material intiygmengandungkodegenetik • Kodegenetiktsbtersimpandlmkromosom • Bdskdayaserapnyathdplarpewarnadibedakanmjd 2 : heterokromatin (menyerapwrn dg kuat) & eukromatin (kurangkuatmenyerapwrn) • Heterokromatinmerupbtkrapat (condensed) drkromatin, shgterlihatsptnodaygrapat. Bnykterlihatsaatselistirahat, sptlimfositatauselmemoriygmenanti antigen asing. Heterokromatininaktifdlmtranskripsi • Eukromatinbbtkhalus, bnyktdptdlmkeadaanaktif (selaktifmelakukantranskripsi). Kromatin

  11. Berdasarkan lokasinya kromatin dibedakan mjd 3 daerah : • Kromatin perinukleolar, berada di sekeliling nukleolus • Kromatin internukleolar, berada dlm nukleolus • Kromatin periferal, berikatan dg selaput sel. Kromatin nukleolar & periferal merup heterokromatin Kromatin

  12. Ditinjau dr peranannya sbg materi genetik, heterokromatin dibagi mjd 2 : heterokromatin fakultatif & heterokromatin konstitutif. • Heterokromatin konstitutif selamanya tdk aktif & tetap dlm keadaan mampat selama daur hdp sel • Heterokromatin fakultatif tdk selamanya berada dlm keadaan mampat. Pd saat ttt secara ajeg kromatin ini terurai & saat terurai mrk dpt disalin • Dr analisis kimia ternyata kromatin tdr dr DNA, RNA & protein. Protein yg tdpt di kromatin tdr dr 2 jenis : histon & non-histon Kromatin

  13. Histon merupakan protein bersifat sangat basa, yg disebabkan oleh adanya asam amino lisin & arginin dlm jml cukup bnyk. • Protein non-histon tdpt lbh dr bbrts jns, bervariasi sesuai dg jenis selnya, mis. Aktin, tubulin, RNA polimerase, asetil transferase dll • 146 pasang basa DNA, 1 oktamer histon. 8 buah histon mbtk oktamer yg tdr dr 4 psg masing2 : H2A, H2B, H3 & H4 • Set 8 histon tsb dsbt nuklosome, 10 nm fibril nukleoprotein. Nukleosome dipisahkan oleh daerah antara 4 nm filamen DNA PROTEIN HISTON

  14. DNA CHROMOSOME

  15. Kromosom • Sblm pembelahan sel (stlh sintesis DNA), kromatin mengalami pembelahan kondensasi mbtk individu kromosom metafase, yg nampak sbg sepasang kromatid (tampak spt 2 pasang lengan)

  16. Jmlh kromosom di dlm sel berbeda2 sesuai jns organismenya • Btk & ukuran kromosom selama mitosis berubah2 , sebag bsr memp 2 lengan & tdpt lekukan dsbt kinetokor / sentromer • Sentromer ini merup tempat melekatnya kromosom pd mikrotubul dr gelendong mitosis & sekaligus sbg pusat pergerakan kromosom pd stadium anafase. • Kromosom tanpa sentromer dsbt kromosom asentrik & umumnya gagal memisahkan diri selama pembelahan sel. • Kromosom saat interfase seakan2 hilang, yg tampak dlm nukleus hanya anyaman filamen halus, dsbt kromatin Kromosom

  17. TTAGGG Gene 1 Gene 2 DNA Telomeres Telomeres Chromosome

  18. 8,000 3,000 1,500 0 35 65 Age (years) Telomere length in base pairs (human white blood cells) Telomere Length Declines

  19. A HISTORY OF DNA SEE p. 292-293 • Discovery of the DNA double helix A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928) B. Rosalind Franklin- X-ray photo of DNA. (1952) C. Watson and Crick- described the DNA molecule from Franklin’s X-ray. (1953)

  20. “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone DNA Double Helix

  21. UNIT FUNGSIONAL DNA/RNA

  22. Perbedaanstrukturgulaantara RNA dan DNA

  23. Basa DNA/RNA

  24. IKATAN RANTAI DNA

  25. IKATAN FOSFODIESTER

  26. G C N N C 5’ O CH 5’ end HC C PO-CH2 NH2 C N N O 1’ 4’ C C CH N NH2 pGCUA 3’ 2’ OH OH OH C CH O O O O N O P O CH2 O P O CH2 O P O CH2 O O O O O O O CH U HN C N C CH C HN O N CH H2N-C C • ribose sugars • Phosphodiester linkages • Directional chain (5’ to 3’) • 4 Bases • purines: adenine & guanine • pyrimidines: cytosine & uracil N N A 3’ OH 3’ end O-H RNA is a polymer of ribonucleotides

  27. DNA/RNA BERSIFAT ANTIPARALEL

  28. DNA Double Helix Guladeoksiribosa Adenine pairs with Thymine (A-T) Tetapadadinukleus RNA Rantaitunggal Gularibosa Uracil replaces Thymine! Ditransportkesitoplasma DNA vs. RNA

  29. G C N N C 5’ O CH 5’ end HC C OPO-CH2 NH2 C N N O 1’ 4’ C C CH N NH2 pGCTA 3’ 2’ C CH O O O O N CH3 O P O CH2 O P O CH2 O P O CH2 C HN O O O O O O O C CH T O N C N C HN CH H2N-C C • 2’-deoxyribose sugars • Phosphodiester linkages • Directional chain (5’ to 3’) • 4 Bases • purines: adenine & guanine • pyrimidines: cytosine & thymine N N A 3’ 3’ end OH DNA is a polymer of2’-deoxyribonucleotides

  30. . . . . . . . . . . . . OH OH O OH OH O O O N N N O O P O-CH2 O P O-CH2 O P O-CH2 O O OH O O O O O O P N O HOCH2 O N O P O CH2 O P OH O O O O + H O O ... ... O P O O P O O O H2O mixture of 2’- and 3’- monophosphate derivatives RNA shortened RNA RNA is easily hydrolyzed under alkaline conditions The reaction proceeds through a 2’,3’-cyclic monophosphate intermediate. Enzymatic hydrolysis of RNA by RNase proceeds through a similar intermediate. Because DNA lacks the 2’-OH group, it is stable under alkaline conditions.

  31. O C H2O uracil cytosine NH2 CH HN C C CH CH N O N C CH O N Cytosine deaminates non-enzymatically to form uracil. If this happens in DNA, it constitutes a mutation. A proof-reading system recognize the error, and replaces the U by C. Why does DNA contain T rather than U? Deamination of cytosine is of little consequence in RNA, which is not the permanent repository of genetic information.

  32. N HO-CH2 O + + + + M M M M O N O P OCH2 O O O O O N O P OCH2 O N O O P OCH2 O O-PO32 5’ A phosphodiester group has a pKa of about 1, and so will always be ionized and negatively charged under physiological conditions (pH ~7). Nucleic acids require counterions such as Mg2+, polyamines, histones or other proteins to balance this charge. The phosphate groups of DNA and RNA are negatively charged 3’

  33. OH HO-CH2 O 5’ H-C=O N HO-CH2 H-C-OH O H-C-OH OH H-C-OH OH OH OH OH O H-C-OH N CH2OH O P O CH2 b-furanose (ring) form O O ribose in its aldehyde form 5’ O N 4’ O P O CH2 O O endo O 1’ 3’ N O P O CH2 C-2’ exo O N O 3’ The ring can adopt various puckered conformations in which C-2’ and C-3’ are in either exo or endo positions relative to the base and C-5’. OH O-PO32 The sugars are always in the b-furanose (cyclic) form

  34. NH2 C N C N N C N C CH HC HC C CH NH2 C N N N N C CH N NH2 HOCH2 HOCH2 HOCH2 HOCH2 C CH O N anti-Adenosine syn-Adenosine O O O O The bases can adopt either syn or anti conformations, but anti conformations are preferred. OH OH OH OH OH OH OH OH NH2 C HC N HC C O N anti-Cytosine syn-Cytosine The nucleotide base can rotate with respect to the sugar