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RNA: extended from 5' to 3'; single-stranded;
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Transcription initiates at promoters: binding of RNA polymerase, accessory proteins
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The process of transcription consists of initiation, elongation, and termination
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5'-capping, 3'-polyadenylation
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Transcription is the synthesis of RNA from a DNA template
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DNA need to be unwrapped from histone core for transcription to proceed
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RNA polymerase adds ribonucleotides to 3'-OH end, following Watson-Crick base pairing
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The RNA strand is complementary and antiparallel to the DNA template.
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U instead of T is used.
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RNA polymerases: enzymes that catalyze the synthesis of RNA
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Accessory proteins: e.g. sigma factor, general transcription factors
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DNA template
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Ribonucleotides
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All RNA come from transcription.
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Only mRNA produce protein.
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mRNA
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Nucleus and cytoplasm
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Carries genetic code for proteins
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tRNA
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Cytoplasm
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Helps incorporate amino acids into polypeptide chain
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rRNA
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Cytoplasm
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Structural and functional components of the ribosome
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1. RNA polymerase binds to promoter DNA sequences
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2. RNA polymerase separates the DNA strand to create a transcription bubble (promoter opening)
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3. Ribonucleoside triphosphate are added
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4. Polymerase moves past the promoter and becomes stably bound to DNA (promoter clearance)
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1. RNA polymerase moves along template strand and elongate the RNA transcript
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2. RNA polymerase unwinds duplex ahead of it to expose single strand template. DNA strands behind RNA polymerase pairs again to reform DNA duplex.
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3. The growing RNA transcript is extruded through the RNA polymerase
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RNA polymerase dissociates from DNA template when it encounters a terminator sequence.
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Longer than mRNA
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1. Addition of 5' cap
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2. Addition of poly(A) tail
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3.RNA splicing
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introns removed, exons spliced together
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