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

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

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.

Types of RNA Messenger 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

Types of RNA Transfer 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

Types of RNA Ribosomal 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

Dictionary of the Genetic Code

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

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

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

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

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

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)

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