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34 Cards in this Set
- Front
- Back
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In bacteria, RNAP transcribes genes for....
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rRNAs, tRNAs, and mRNAs.
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In prokaryotes several genes with associated functions are grouped together on a chromosome and....
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transcribed as one unit called a polycistronic transcript.
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_____ genes are transcribed as a group and then cut apart/modified.
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tRNA and rRNA
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tRNA genes are used for...
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binding to amino acids and bringing them to a ribosome so a messenger rna can be translated into a protein.
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Polycistronic mRNAs in bacteria contain....
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multiple genes that are co-transcribed, with protein-coding regions that are each transcribed simultaneously.
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Eukaryotic mRNAs are.....
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monocistronic (1 gene/transcript) that contain introns that interrupt the coding sequence and mus be removed before the mRNA can be translated.
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The alpha units of the structure of E. coli RNAP does what?
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Used in the recognition of DNA at promoters
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The beta and beta' units of the structure of E. coli RNAP does what?
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they make contact with the strands of DNA, bind nucleotides and chemically make the complimentary strand of RNA.
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The RNAP core binds to DNA in the ____ mode.
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non-active
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The RNAP core can _____ after initiation, but cannot ________.
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transcribe DNA to RNA; initiate transcription.
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The RNAP core + σ (sigma) subunit yields...
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an active RNAP holoenzyme.
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What does the RNAP holoenzyme do?
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It binds an initiates gene transcription at promoters.
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What happens to the cor after transcription has begun?
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The sigma unit disassociates and the core continues to make RNA from DNA.
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How is the numbering of bases relative in the promoter region? What occurs to the left or right?
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By the start of the transcript at +1. Transcription occurs to the right and the numbering is +2, +3, etc. To the left is negative (promoter region).
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-35 region sequence is
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TTGACA
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-10 region sequence
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TATAAT
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What is specific about the TATAAT box?
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It is also called the Pribnow box. It is the first to be 'melted' and is unwound by holoenzyme.
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What subunits react with what regions?
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sigma reacts with both -10 & -35; alpha only makes contact with -35.
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In transcription, when the enzyme core binds, what occurs?
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A closed complex is formed. This means the DNA is not separated immediately.
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Two different complexes are formed once the core enzyme is bound. What are they?
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1. When 10-12 bp are melted, they create short polyribonucleotides and release them.
2. When more bp are melted RNAP can proceed to transcribe the gene and sigma is released. |
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RNA polymerase complex slides along DNA creating ______ as it moves along.
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an open complex
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The _____ strand is used to make a complimentary copy of RNA.
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template
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RNA is synthesized in the __-->__ direction that uses ____ as precursors and releases _____.
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5'-->3'; ribonucleoside triphosphates; pyrophosphate
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In transcription, the same AT/GC rules apply except...
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U is substituted for T.
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In transcription, no _____ is needed.
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primer or helicases
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Energy for elongation is derived from....
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hydrolysis of high energy phosphate bonds.
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In transcription of eukaryotes,....
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they have 3 RNAPs.
RNAP I transcribes only rRNAs. RNAP II transcribes only mRNAs. RNAP III makes small RNAs. And many accessory factors are needed to initiate transcription. |
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In transcription in Archaea,....
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they have a single RNAP similar to Euk RNAP II. They use accessory factors and have promoters that resembly Euk promoters.
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Eukaryotic mRNAs...
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have a 3'polyA tail, a 5'cap added post-transcriptionally, and all introns are removed before translation.
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Two ways to terminate transcription in bacteria.
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Hairpin and ρ-dependant termination
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Explain how hairpins terminate transcription.
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a hairpin is formed followed by a poly U sequence. This then allows ρ-independent intrinsic termination.
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Explain ρ-dependent termination.
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It does not require a hairpin, but it does require ATP and ρ.
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As soon as mRNAs are beginning to be transcribed, ribosomes....
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attach and begin to translate them into proteins.
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What is the correlation with transcription/translation and speed?
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Translation keeps up with Transcription and is relatively slow (transcrip = 45-75 bp/sec; transla = 15-30 AA/sec, but 3 or 4 AA are made at at time).
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