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17 Cards in this Set
- Front
- Back
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RNA Polymerase and Transcription concept
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E. coli RNA polymerase consists of α, β, β�, ω, and σ subunits. Transcription is initiated by the binding of σ to promoter sequences. After synthesis of about the first ten nucleotides of RNA, the core polymerase dissociates from gamma and travels along the template DNA as it elongates the RNA chain. Transcription then continues until the polymerase encounters a termination signal.
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Repressors and Negative Control of Transcription concept
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The prototype model for gene regulation in bacteria is the lac operon, which is regulated by the binding of a repressor to specific DNA sequences overlapping the promoter.
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Positive Control of Transcription
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Some bacterial genes are regulated by transcriptional activators rather that repressors
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Eukaryotic RNA Polymerases concept
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Eukaryotic cells contain three distinct nuclear RNA polymerases that transcribe genes encoding mRNAs and miRNAs (polymerase II), rRNAs (polymerases I and III), and tRNAs (polymerase III).
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General Transcription Factors and Initiation of Transcription by RNA Polymerase II
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Eukaryotic RNA polymerases do not bind directly to promoter sequences; they require additional proteins (general transcription factors) to initiate transcription. The promoter seqeunces of genes transcribed by RNA polymerase II are recognized by the general transcription factor TFIID, which recruits additional transcription factors and RNA polymerase to the promoter.
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Transcription by RNA Polymerases I and III concept
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RNA polymerases I and III also require additional transcription factors to bind to the promoters of rRNA, tRNA, and some snRNA genes
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_____ is the first step in gene expression and is the initial level at which gene expression is regulated.
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Transcription
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____ in eukaryotic cells are then modified and processed in various ways.
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RNAs
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An understanding of transcription in ____ has provided the foundation for studies of the far more complex mechanisms that regulate gene expression in eukaryotic cells.
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E. coli
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______ catalyzes polymerization of ribonucleoside 5'-triphosphates (NTPs), as directed by a DNA template, always in the 5' to 3' direction
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RNA Polymerase
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Transcription initiates ______ at specific sites. This is a major step at which regulation of transcription occurs.
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de novo
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What is the term when no preformed primer is required
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de novo
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_____ polymerase has five subunits
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Bacterial RNA polymerase
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The ____ subunit is weakly bound and can be separated from the others. it is required to identify the correct sites for transcription initiation.
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σ or gamma
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Most bacteria have several different gammas that direct RNA polymerase to different start sites under different conditions
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Most bacteria have several different gammas that direct RNA polymerase to different start sites under different conditions
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The _____ is the gene sequence to which RNA polymerase binds to initiate transcription.
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promoter
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promoters have six nucleotides and are located at ___ and ____ base pairs upstream of the transcription start site.
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10 and 35
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