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Genetic Information Flow: RNA Structure

Genetic Information Flow: RNA Structure . YILDIRIM BEYAZIT UNIVERSITY FACULTY OF MEDICINE THE DEPARTMENT OF MEDICAL BIOLOGY ASST. PROF. DR. ENDER ŞİMŞEK. Central Dogma. Nucleic Acids. DNA ( Deoxyribonucleic acids ). RNA ( Ribonucleic acids ). NUCLEIC ACIDS. RNA .

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Genetic Information Flow: RNA Structure

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  1. Genetic Information Flow: RNA Structure YILDIRIM BEYAZIT UNIVERSITY FACULTY OF MEDICINE THE DEPARTMENT OF MEDICAL BIOLOGY ASST. PROF. DR. ENDER ŞİMŞEK

  2. Central Dogma

  3. NucleicAcids DNA (Deoxyribonucleicacids) RNA (Ribonucleicacids) NUCLEIC ACIDS

  4. RNA 3 Hydrogen Bonds – more stable 2 Hydrogen Bonds • RNA bases: A,G,C,U • Canonical Base Pairs • A-U • G-C • G-U “wobble” pairing

  5. Different bases in RNA and DNA RNA only DNA only DNA and RNA

  6. RNA chain is made single stranded!

  7. PROKARYOTE

  8. EUKARYOTE

  9. Pulse-chaseexperimentwithradiolabeledUracil in E. Coli

  10. RNA Molecules

  11. HairpinStructure RNA Structures in Different RNA Viruses

  12. RNA mRNA (messengerRNA) tRNA (transfer RNA) rRNA (ribosomalRNA) Three RNA Molecules

  13. RNA structure RNA Pyrimidine (C4N2H4) Purine (C5N4H4) Adenine Uracil Cytosine Guanine Thymine (DNA) Uracil (RNA) Nucleoside Nucleotide base + sugar (ribose) base + sugar + phosphate 3 major types of RNA messenger RNA (mRNA); template for protein synthesis transfer RNA (tRNA); adaptor molecules that decode the genetic coderibosomal RNA (rRNA); catalyzing the synthesis of proteins ribonucleic acid 4 bases A = U = C = G =

  14. Base interactions in RNA Base pairing: U/A/(T) (2 hydrogen bonds) G/C (3 hydrogen bonds) RNA base composition: A + G = U + C / Chargaff’s rule does not apply (RNA usually prevails as single strand)

  15. A) single stranded regions B) duplex C C) hairpin D) internal loop D E) bulge loop G E F F) junction B A G) pseudoknot RNA structure Primary structure formed by unpaired nucleotides Secondary structure double helical RNA (A-form with 11 bp per turn) duplex bridged by a loop of unpaired nucleotides nucleotides not forming Watson-Crick base pairs unpaired nucleotides in one strand,other strand has contiguous base pairing three or more duplexes separated by singlestranded regions tertiary interaction between bases of hairpin loopand outside bases

  16. RNA structure Primary structure Secondary structure Tertiary structure C D G E F B A

  17. RNA 1. mRNA (messengerRNA) 2. tRNA (transfer RNA) 3. rRNA (ribosomalRNA) Three RNA Molecules

  18. 1- Messenger RNA (mRNA): • comprised only 5% of total cellular RNA. • Function: Carry genetic information from DNA in the nucleus to ribosomes (in cystol) where it is used as template for protein biosynthesis.

  19. messenger RNA

  20. mRNA is synthesized in thenucleus Singlestrandedhelix in shape Carrygeneticinformationfrom DNA tocytosol Copiedgeneticinformationcalled as transcription Containsno H bonds

  21. EukaryoticmRNAcodesfor a single protein-Monosistronic ProkaryoticmRNAcodesformanyproteins-Polysistronic

  22. mRNAProcess in Eukaryotes mRNA is synthesized as a pre-mRNA form. Processstepsare: After capping of 5’ end of mRNA, 20-30 ntmRNA is synthesizedand 7-metylguanosine is added on thisend. The role of thisstructure is tobindtoribosomes.

  23. mRNAProcess in Eukaryotes • mRNA is synthesized as a pre-mRNA form. Processstepsare: • After capping of 5’ end of mRNA, 20-30 ntmRNA is synthesizedand 7-metylguanosine is added on thisend. The role of thisstructure is tobindtoribosomes. • PolyA tail (50-250 A nt) is added on to 3’ end of mRNA. Thisstructure is importantfortermination of transcriptandstability of mRNA.

  24. The pre-mRNA molecule undergoes three main modifications. These modifications are 5' capping, 3' polyadenylation, and RNA splicing, which occur in the cell nucleus before the RNA is translated.

  25. 2- Ribosomal RNA (rRNA): • In the cell, 80 % of total RNA are rRNA. • rRNA are found in combination with several proteins as component of the ribosome which is the site of protein synthesis.

  26. RNA 1. mRNA (messengerRNA) 2. rRNA (ribosomal RNA) 3. tRNA (transfer RNA) Three RNA Molecules

  27. 2- Ribosomal RNA (rRNA): • In Eucaryotic(mammals): • There are 4 size types of rRNA (5S, 5.8S, 18S and 28S) representing 2/3 particle mass of the ribosome. • In procaryotic (bacterias): • There are 3 size species of rRNA (5S, 16S and 23S)

  28. Ribozomal RNA • Synthesized in nucleus. • 80% of total RNA in the cytoplasm. • The main structural element of the ribosomes (approximately 65%). • Decoding the genetic codes of mRNA in ribosomes. • Play a role in all kinds of protein synthesis. • Re-used many times. • There are weak hydrogen bonds in its structure.

  29. ProkaryoticrRNA;

  30. EukaryoticrRNA;

  31. rRNA (RibosomalRNA) Svedberg Units

  32. RNA 1. mRNA (messengerRNA) 2. tRNA (transfer RNA) 3. rRNA (ribosomalRNA) Three RNA Molecules

  33. 3- Transfer RNA (tRNA): tRNA represents 15% of total RNA in the cell. Structure: 1- amino acid attachment site or amino acid acceptor: which terminates with the triplet CCA.

  34. 3- Transfer RNA (tRNA): tRNA represents 15% of total RNA in the cell. Structure: 1- amino acid attachment site or amino acid acceptor: which terminates with the triplet CCA. 2- Anticodon loop or anticodon triplet

  35. 3- Transfer RNA (tRNA): tRNA represents 15% of total RNA in the cell. Structure: 1- amino acid attachment site or amino acid acceptor: which terminates with the triplet CCA. 2- Anticodon loop or anticodon triplet. 3- D loop and T loop: contain unusual bases e.g. dihydro-uracil, ribothymidine or methyl guanine.

  36. Functions of tRNA: 1- transport amino acids to ribosome for protein synthesis. Each tRNA carry only one amino acid. The specific amino acid is attached enzymatically to 3' end of tRNA.

  37. Functions of tRNA: 2- recognize the specified codon on mRNA to ensure the insertion of the correct amino acid in the growing polypeptide chain. This function is due to anticodon triplet which binds to codon on mRNA by base pairing.

  38. (Three nucleotide bases on mRNA form a codon which is then translated into specific amino acid.)

  39. The smallest RNA. • Specificforoneaminoacid. • Re-usedfordifferent protein synthesis. • At least 20 kinds of tRNA in cells.

  40. The synthesis of mature tRNA

  41. RNA structure:3 levels of organization Primary: Covalent bonds • Secondary/Tertiary • Non-covalent bonds • H-bonds • (base-pairing) • Base stacking

  42. Common structural motifs in RNA • Helices • Loops • Hairpin • Interior • Bulge • Multibranch • Pseudoknots

  43. Pseudoknot. Thepseudoknotstructure is formed by base pairingbetweennoncontiguouscomplementarysequences. (a) hairpin (b) bulge (c) loop

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