Prok trans.ppt
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This document discusses the process of transcription, where DNA is used as a template to produce RNA. It begins with initiation, in which RNA polymerase binds to promoter sequences on DNA and forms an open complex. This allows elongation to occur, where RNA is synthesized using the DNA as a template. Termination occurs when the polymerase reaches terminator sequences. Key aspects covered include the transcription bubble, holoenzyme formation, sigma factors, promoter and terminator sequences, and the channels of RNA polymerase.
Prok trans.ppt
- 1. The synthesis of RNA molecules using DNA strands as the templates so that the genetic information can be transferred from DNA to RNA. Transcription
- 2. • The whole genome of DNA needs to be replicated, but only small portion of genome is transcribed in response to the development requirement, physiological need and environmental changes. • DNA regions that can be transcribed into RNA are called structural genes.
- 3. Transcriptional Control DNA RNA protein Transcription Initiation Elongation Termination Processing Capping Splicing Polyadenylation Turnover Translation Protein processing Many places for control
- 4. 1.1 Template The template strand is the strand from which the RNA is actually transcribed. It is also termed as antisense strand. The coding strand is the strand whose base sequence specifies the amino acid sequence of the encoded protein. Therefore, it is also called as sense strand.
- 5. G C A G T A C A T G T C 5' 3' 3' C G T C A T G T A C A G 5' template strand coding strand transcription RNA G C A G U A C A U G U C 5' 3'
- 7. Initiation RNA polymerase core subunits (α α’ β β’ ω) Sigma factor (σ) Core + σ = holoenzyme Binds promoter sequence Catalyzes “open complex” and transcription of DNA to RNA
- 8. TRANSCRIPTION PROCESS: INITIATION ELONGATION TERMINATION “Closed Complex” “Open complex” (~14 bps) (Transcription initiation is considered complete when the first two ribonucleotides of an RNA chain are linked by a phosphodiester bond.)
- 9. (primary transcript) TRANSCRIPTION PROCESS: INITIATION ELONGATION TERMINATION
- 10. The Holoenzyme: Direction of transcription Upstream Downstream Prokaryotic RNA polymerase -Core pol + 70 factor = RNA Pol Holoenzyme -70 factor recognizes and binds to the promoter region
- 11. Bacterial sigma factors Sigma factors are “transcription factors” Different sigma factors bind RNAP and recognize specific -10 ,-35 sequences Helps melt DNA to expose transcriptional start site -10 (binding and melting of DNA ) : Pribnow box (prok.) : Hogness box (euk.) -35 (recognition seq. for binding of polymerase)
- 12. Promoter and terminator sequences of a gene tell the RNA polymerase where to start and stop transcription
- 13. 5 channels of enzyme NTP uptake channel RNA exit channel Downstream DNA channel Non template strand (NT) channel Template strand (T) channel