Transcription

Transcription

1. What is Transcription?

   • A section of DNA is decoded to create proteins, to create RNA

2. Differences from DNA Replication

   • Does not use SSB proteins
   • Only small section of DNA strand is broken
   • The RNA nucelotides have different sugar and uracil replaces thymine
     • Also single stranded
   • No Helicase needed

3. What are the sequence of events?

   • Elongation
     • The RNA Polymerase causes the alpha subunit of ribose to phosphodiester bond with -OH on the 3rd carbon. A pyrophosphate is lost
       • The RNA polymerase breaks open the RNA strand at -10 box
   • Initiation
     • Eukaryotes
       • Uses TATA box
       • Uses TF's (DABFEH)
       • RNA Polymerase II
     • Prokaryotes
       • Uses -35, -10 and +1 Box
       • RNA Polymerase attaches to the promoter region covering from -35- +1
   • Termination
     • A terminator region is reached as a result a stem loop forms. The RNA polymerase gets tangled with the stem loop and broken off
       • They are palindromes and RNA base pair itself
       • Factor Row
       • After this RNA can go straight into translatin
     • Prokaryotes
     • Eukaryotes
       • Pre-RNA is formed and further spliced into RNA
         • There are three parts to this: Capping, Polyadenylation and Intron Splicing
           • Capping
             • Guanine bond joined by 5 - 5 prime tri phosphae bond on 5 prime end base of the pre-MRNA
               • The guanine is then methylated
           • Polyadenylation
             • Signal reached, cleaved 10-30 bases downstream, 250 adenine bases added
           • Intron Splicing
             • Uses snRNP
               • OH on 2 prime carbon nucleophilic attack on 5 prime end of intron
                 • The 5 prime -OH attackes 3 prime intron end of intron and a lariat forms

4. Structure of RNA Polymerase

   • Made up of five subunits, sigma subunit can detach to create a four subunit core enzyme
   • Sigma subunit tells RNA polymerase where promoter region starts

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