Term
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Definition
| synthesizes mRNA in 5' -> 3' direction b/c moves along DNA template in 3' -> 5' direction; unlike DNA polymerase, doesn't need primer to start transcription; only uses one of two DNA strands as template; large, globular and has several prominent channels running through interior (enzyme's active site, where phosphodiester bonds form, is located where several channels intersect) |
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Term
| non-template strand also known as ____ |
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Definition
| coding strand b/c matches RNA (except U instead of T) |
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Term
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Definition
| detachable protein subunit; makes initial contact with DNA that starts transcription in bacteria (not RNA polymerase); regulatory in nature (tells RNA polymerase where and when to start synthesizing RNA); released once RNA synthesis is started; most bacteria have several types of this, each with distinctive structure and function (identity of sigma protein determines which types of genes will be transcribed) |
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Term
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Definition
| sections of DNA where transcription begins; binding sites between holoenzyme and DNA; located on non-template strand; 40-50 base pairs; have a particular section that looks similar, (-10 box, TATAAT) and another sequence centered about 35 bases upstream from +1 site (-35 box, TTGACA) |
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Term
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Definition
| six-base pair sequence that is centered about 10 bases from point where RNA polymerase begins transcription |
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Definition
| place where transcription begins |
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Term
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Definition
| DNA that is located in direction RNA polymerase moves during transcription |
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Definition
| DNA that is located in the opposite direction RNA polymerase moves during transcription |
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Term
| ribonucleoside triphosphates (NTPs) |
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Definition
| like dNTPs; enter a channel at the bottom of enzyme and diffuse to active site |
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Term
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Definition
| consists of a core enzyme (RNA polymerase), which contains active site for catalysis, and other required proteins; made of RNA polymerase and sigma |
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Term
| transcription begins when _____ |
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Definition
| sigma, as pat of the holoenzyme complex, binds to the -35 and -10 boxes (initiation phase) |
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Term
| after sigma binds to a promoter, _____ |
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Definition
| DNA helix opens, template strand is threaded through a channel that leads to the active site inside RNA polymerase (initiation phase) |
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Term
| RNA polymerization begins when _____ |
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Definition
| an incoming NTP pairs with a complementary base on template strand of DNA - catalzyed by RNA polymerase, exergonic, spontaneous b/c NTPs have so much energy from 3 phosphate groups (initiation phase) |
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Term
| transcription occurs when ______ |
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Definition
| RNA polymerase matches base in NTP with complementary base in a gene, then RNA polymerase catalyzes formation of phosphodiester bond (initiation phase) |
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Term
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Definition
| group of projecting amino acids that help open double helix at upstream end (elongation phase) |
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Term
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Definition
| nearby group of amino acids that help steer template and non-template strands through channels inside enzyme (elongation phase) |
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Term
| enzyme's active site catalyzes addition of ______ |
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Definition
| nucleotides to 3' end of growing RNA molecule (elongation phase) |
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Term
| during elongation, all prominent channels or grooves in enzyme are _______ |
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Definition
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Term
| double-stranded DNA goes into and out of one groove; NTPs enter another; growing RNA strand exits to the rear |
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Definition
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Term
| transcription stops when _____ |
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Definition
| RNA reaches a stretch of DNA sequences that functions as transcriptional terminal signal (termination phase) |
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Term
| bases that make up transcription terminal signal have unusual property |
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Definition
| as soon as it is synthesized, RNA sequence folds back on itself and forms a short double helix that is held together by complementary base pairing - secondary structure that results is hairpin - formation of hairpin disrupts interaction between RNA polymerase and RNA transcript, resulting in the physical separation of the enzyme and its product |
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Term
| summary of transcription in bacteria |
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Definition
| Transcription begins when sigma, as part of the holoenzyme complex, binds to the promoter at the start of a gene. Once binding occurs, RNA polymerase begins to synthesize mRNA by adding ribonucleotides that are complementary to the template strand in DNA. Transcription ends when a termination signal at the end of the gene leads to the formation of a hairpin in the mRNA, disrupting the transcription complex. |
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Term
| nucleotides are added to the ____ end of RNA |
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Definition
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Term
| function of -35 and -10 box in bacterial promoters |
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Definition
| bind the sigma subunit that is associated with RNA polymerase |
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Term
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Definition
| (1) Sigma binds to RNA polymerase. (2) Sigma binds to the promoter region. (3) The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. (4) Transcription begins. (5) Sigma is released. |
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| different eukaryotic RNA polymerases |
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