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RNA Structure and Transcription

RNA Structure and Transcription. Joyce Fiel Matt Speir Alliver Verzon Shann Bunggay. Overview. RNA Structure Types of RNA mRNA tRNA rRNA The Genetic Code [Codons] Transcription Initiation Elongation Termination. What is RNA?. RNA = Ribo Nucleic Acid Single Strand

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RNA Structure and Transcription

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  1. RNA Structure and Transcription Joyce Fiel Matt Speir Alliver Verzon Shann Bunggay

  2. Overview • RNA Structure • Types of RNA • mRNA • tRNA • rRNA • The Genetic Code [Codons] • Transcription • Initiation • Elongation • Termination

  3. What is RNA? • RNA = Ribo Nucleic Acid • Single Strand • Similar to DNA but pyrimidyne base, uracil replaces thymine and ribose replace deoxyribose • Five-carbon sugar • Nucleotides: Guanine, Cytosine, Adenine, Uracil • Backbone made of alternating ribose and phosphate groups • Other bases: thymine, pseudouridine and methylated cytosine and guanine.

  4. Types of RNAMessenger RNA (mRNA) • Transcribed from DNA template • Carries coding information to ribesome (site of protein synthesis) • Moves DNA information to translation machinery • Always has 5’ cap between two modified nucleotides • Most have poly-Adenosine tail at 3’ end • Provides templates used to make amino acids

  5. Types of RNATransfer RNA (tRNA) • Short RNA molecule • also called anticodon or adaptor molecule.  • One or more tRNAs for each amino acid • 3’ end of tRNA attaches to amino acid • Decodes information in DNA • More than 20 different tRNA molecules • Each have between 75-95 nucleotides • 4 arms, 3 loops

  6. Types of RNARibosomal RNA (rRNA) • Most abundant – 80% of RNA • Building blocks of ribosomes • Combines with proteins from cytoplasm to make ribosomal subunits • 3’ end attaches to an amino acid • Several roles in protein synthesis • Catalytic role • Recognition role • Structural role

  7. Dictionary of the Genetic Code

  8. Transcription http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

  9. Transcription Animation http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

  10. What is Transcription? • first step in protein synthesis • DNA-directed synthesis of RNA • Utilizes enzyme called RNA Polymerase • Takes place in 3 stages • Initiation • Elongation • Termination

  11. Stage I:Initiation and RNA Polymerase Binding • Takes place in promoterregion of DNA • RNA polymerase attaches, transcription initiated • DNA unzips • Binding polymerase is different between prokaryotes and eukaryotes • Transcription factorsrequired • Results in transcription initiation complex • TATA box :crucial promoter DNA sequence

  12. Stage II: Elongation of the RNA Strand • DNA continues to unwind • Takes place in coding region of DNA • 10-20 DNA bases exposed to pair with RNA nucleotides • Enzyme adds nucleotides to 3’ end of RNA molecule • DNA double helix reforms, RNA peels away • Transcription in eukaryotes- 60 nucleotides per second • Multiple RNA polymerase can transcribe a single gene simultaneously

  13. Stage III: Termination of Transcription • Transcription stops when RNA hits the terminator DNA sequence • RNA sequence makes actual termination signal (stop codon) • In prokaryotes: transcriptions stops at end of termination signal • In eukaryotes: mRNA is cut free from enzyme about 10-35 nucleotides after termination signal (AAUAAA sequence in pre-mRNA)

  14. Works Cited • http://cnx.org/content/m11416/latest/transcription_initiation.jpg • http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04/RNA_sstrand.jpg • http://academic.brooklyn.cuny.edu/biology/bio4fv/page/antico.htm • http://www.ndsu.edu/instruct/mcclean/plsc731/transcript/transcript1.htm • http://www.johnkyrk.com/DNAtranscription.html • Trusty Bio book • Cliffnotes

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