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Ingredients needed for transcription in bacteria
- DNA template: to serve as a blueprint for the RNA sequence
- Ribonucleotides: to serve as a monomers for RNA polymerization
- RNA Polymerase: catalyses synthesis of RNA
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Naming of parts
- Promoter: extremely important for the recognition of the RNA
- +1 site: site is sort of what is called the start of the transcription
- Coding sequence: region of gene that codes for the protein
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sense strand vs anti-sense strand
sense strand is the nontemplate strand, the anti-sense strand is the template strand
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Initiation of transcription in prokaryotes
1. Polymerase binds to promoter sequence in duplex DNA. "closed complex"
2. Polymerase melts duplex DNA near transcription start sit, forming a transcription bubble. "Open complex"
3.Polymerase catalyzes phosphodiester linkage of two initial rNTPs
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Elongation in Prokaryotes
Polymerase advances 3'to5' down template strand, melting duplex DNA and adding rNTPs to growing RNA
During transcription we transiantly produce a funky hybrid of DNA and RNA
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Formation of phosphodiester bond
Polymerization involves the formation of a phosphodiester linkage between the free 3' hydroxyl of the growing RNA chain and the alpha phosphate group of the incoming rNTP
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Termination
At transcription stop site, polymerase releases completed RNA and dissociates from DNA
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Holoenzyme?
Holoenzyme scans along the DNA until it encounters a promoter region to bind to and form a closed complex.
Consist of core enzyme and sigma actor.
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Task of sigma factor
- Found in the Holoenzyme
- Its task is to find the promoter
- "find where the gene is"
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Alpha subunit and Beta subunit are important in terms of....
They are important in terms of catalysis
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Omega does what?
Is there for stabilizing
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Why is B' (beta prime) important
Important to grab DNA onto the template
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How does the Sigma (σ) factorrecognize the promoter region?
by binding to specific sequence motifs, whic  h areessential for promoter activity (the -10 and -35 regions)
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Translation
Process in which messanger RNA is translated into proteins
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Three roles of RNA
mRNA: Genetic information DNA in form of codons
tRNA: key to decipher the codons in mRNA. Each tRNA has an associated amino acid and anticodon
rRNA: associates with proteins to form ribosomes
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What is never translated?
tRNA and rRNA, there functional identity is to transcript
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Prokaryotes subunits are made of what?
rRNA and proteins
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Initiation of Prokaryotic translation
- Initiation Factors (IFs) associate with the 30S subunit forming the preinitiation complex
- IF1 and IF3 assists the loading of mRNA and the initiation aminoacyl-tRNAforming the 30S initiation complex which binds the transcript at the initiationcodon, AUG
- IF1 and IF2-GTP facilitate theloading of the 50S subunit forming the 70S initiation complex
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Elongation in Prokaryotic translation
- Elongation Factors (EFs) arerequired for the stepwise additionof amino acids
- It’s a ribozyme - the 23S rRNA -that carries out thepeptidyltransferase reaction
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Termination in Prokaryotic translation
- When the mRNA ribosome-tRNA-peptidyl complex reaches a stopcodon, Release Factors(RFs) mediate thetermination of proteinsynthesis.
- RF1 and 2 mimic tRNA
- RF3-GTP catalyzes the cleavage of the peptidyl tRNA releasing the protein chain
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When can you start translation
Not until those tRNA molecules are coupled with their bonded amino acids forming an Amimoacyl-tRNA
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Wobble base pair in the first, or wobble position of anticodon
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Wobble base pairs in third or wobble, position of codon of an mRNA
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