Chapter 8

Chapter 8 - Chapter 8- Transcription, Translation, and...

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Chapter 8- Transcription, Translation, and Bioinformatics RNA Synthesis Transcription- making an RNA copy of part of a DNA strand DNA- made of deoxyribonucleotides (missing an oxygen that ribonucleotide has) Double stranded Thymine Sugar- deoxyribose RNA- made of ribonucleotides Single Stranded (can fold on itself and create an area of double-strandedness, but not typical) Uracil Sugar- Ribose Three types of RNA: 1. mRNA ____________ Contains info to make proteins 2. tRNA ____________ a. Carries amino acids to build the polypeptide during translation 3. rRNA ____________ a. Component of ribosomes (site of protein synthesis) Template strand- DNA strand that is being copied into complementary mRNA RNA polymerase- enzyme that transcribes DNA into RNA 1
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Bacterial RNA polymerase 4 subunits: a (2 copies), b, b’, s (greek letters. When the first three are together it’s the core enzyme. When all four are attached it’s called a holoenzyme. The sigma factor comes and goes. Process of transcription 3 phases: 1. Initiation 2. Elongation 3. Termination Transcription of RNA from DNA involves the enzyme RNA polymerase , which adds ribonucleotides onto 3’ end of growing RNA chain Unlike DNA polymerase, RNA polymerase needs no primer RNA polymerase recognizes a specific start sequence on the DNA called the promoter and starts transcribing DNA into RNA at that site. Does not occur just randomly, has to start at the right place so the mRNA will be correct sequence and protein will be correct sequence. Transcription Initiation Sigma factor binds core RNA polymerase Forms RNA polymerase holoenzyme RNA polymerase binds promoter Sequence on DNA 10 and 35 bases upstream of start site Polymerase unwinds DNA at promoter Open complex 2
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Sigma factor released Promoters Specific DNA sequences indicating start site of transcription Two important regions: (in Bacteria ) -35 sequence -10 sequence (Pribnow box) (- means upstream of start site) Prokaryotes have a single RNA polymerase with a sigma subunit. The sigma factor binds to the promoter to initiate transcription. Multiple sigma factors S 70 Guides RNA polymerase to most genes S32 Active when cell is stressed by heat Heat-shock response Transcription Elongation Core RNA polymerase moves down the template DNA strand from 3’ to 5’ RNA strand is made 5’ to 3’ (ribonucleotides are added to the 3’ end)-complementary to the DNA 3
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Transcription Termination When RNA polymerase reaches terminator (not the terminus that ends DNA replication), transcription stops and RNA chain is released. Polymerase slows at pause site
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This note was uploaded on 05/07/2011 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

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Chapter 8 - Chapter 8- Transcription, Translation, and...

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