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Chapter 11 - Transcription and Translation

Termination transcription factors are crucial for

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Unformatted text preview: rs are crucial for function of all 3 types of polymerases all 3 types of RNA are made from precursor RNA that is longer than the final RNA product Initial precursor RNA is equal in length to the DNA transcribed primary transcript (pre-RNA) Pre-RNA exists for a very short period of time, usually processed into functional RNAs by a series of reactions Eukaryotic Transcription- mRNA o o o o o o o o o o o Experiment: ekaryotic cells incubated with radioactive uridine (which forms U in RNA) If killed immediately, labelled RNA: have large molecular weights, diverse (heterogeneous) nucleotide sequence, they are found only in the nucleus heterogeneous nuclear RNAs (hnRNAS) Cells imaged several hours later: most radioactivity now in smaller mRNAs in cytoplasm hnRNAS are primarily precursors to cytoplasmic mRNAs all eukaryotic mRNA precursors are synthesized by RNA polymerase II RNA polymerase II binds the promoter in complex with a number of general transcription factors (GTFs) forms preinitiation complex (PIC) Promoter elements lie upstream (5 )of transcription start site Most genes have TATA box 25 to 35 bases upstream of intiation site consensus sequence TATTAA, effects transcription rate, determines location of transcript initiation General transcription factors (GTFs) transcription factor for polymerase II is TFII TFIID (TFII, fraction D) recognizes the TATA box preinitiation complex assembles at the TATA box; smaller TATA-binding protein (TBP) within TFIID binds the TATA seque...
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