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40 Cards in this Set
- Front
- Back
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Review; what is TRANSCRIPTION?
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The process of copying DNA into mRNA.
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What is TRANSLATION?
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The process of making protein products out of the mRNA.
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What type of RNA gets translated? What types don't?
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mRNA gets Translated.
tRNA, sRNA, and rRNA don't. |
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What is the central feature to remember about Transcription?
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It is highly SELECTIVE - some sequences are transcribed, but not ALL.
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How is it that Transcription is so selective?
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Very specific signals embedded in DNA tell where and when to start and stop transcription.
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List the 3 major types of RNA, state its % and complexity:
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mRNA - 5% most complex
tRNA - 15% rRNA - 80% least complex |
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How do most RNA molecules exist in the cell?
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As single strands - not a double helix like DNA.
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Where are rRNA molecules found?
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In RIBOSOMES
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What are Ribosomes?
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Complex structures - sites of protein synthesis.
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What are the 3 size species of rRNA in proks?
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-23S
-16S -5S |
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What are the 4 rRNA size species in the eukaryotic cytosol?
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28S
18S 5.8S 5S |
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What is S?
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the Svedburg unit; relates mw and shape of the rRNA.
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Which type of RNA is smallest?
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tRNA.
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How many residues are commonly in tRNA?
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74-95
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What are 2 unique qualities of tRNA?
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-They have unusual bases
-Have extnsive intrachain base-pairing. |
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How many tRNA molecules are there?
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At least one specific type for each of 20 amino acids.
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Which end of a tRNA molecule carries:
-The amino acid? -The binding code for mRNA? |
3' end - amino acid
Anticodon loop - anticodon |
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What is the Major Function of mRNA?
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Carrying genetic information from the nuclear DNA to the cytosol for protein synthesis.
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What characteristics make eukaryotic mRNA unique from Prokaryotic?
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-5'-5' CAP - 7methylguanosine
-3' PolyA Tail |
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What is a PROMOTER REGION?
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A sequence (at the beginning of a DNA sequence for transcriptn) that is recognized by RNA Pol
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What is a Termination Region?
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Similar to the promotor region but tells RNA Polymerase to stop transcription.
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In what direction is RNA sequenced during transcription?
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5' -> 3'
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What are the subunits in the Core enzyme RNA Polymerase?
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2 alpha
1 Beta 1 Beta' 1 w (omega) |
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What makes up the holoenzyme RNA Polymerase?
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The Core subunits + Sigma
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What is the function of the sigma subunit in RNA Pol?
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Confers specificity for recognizing various promotor regions of DNA.
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What is the function of the core portion of RNA Pol?
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Polymerization of the RNA.
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What TYPE of an enzyme is RNA polymerase?
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a Zinc Metalloenzyme - requires Zn2+.
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What is rho (p) factor?
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A termination factor in E. coli that signals transcription to stop.
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What are the 3 main Phases of transcription in E. coli?
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1. Initiation
2. Elongation 3. Termination |
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What is a Promotor site again?
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The sequence where RNA Pol binds to start transcription.
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What is the Operator site?
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A site near the Promotor, but it has binding sites for activation or repression of the gene.
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What component of RNA Pol is responsible for binding the Promotor site again?
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Sigma.
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How many genes intended for translation are usually in the DNA being transcribed in bacteria?
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Many - polycystronic.
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What is an Operon?
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The combined name for the Promotor, Operator, and Structural genes in bacteria.
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What is the Pribnow box, really?
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The name for the Standard promotor found in bacterial genes.
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Where is the Pribnow box located?
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-10 nucleotides from the start of transcription.
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What is the Pribnow box sequence?
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TATAAT
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What key info should be remembered re: bacterial promotor regions?
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Consenses sequences are highly conserved - the promotors are very similar, but not identical allowing varied gene expression.
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Are all consenses sequences (promotors) recognized by the same sigma factor?
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No; there are different sigma factors for different operators.
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What other sequence is an important promotor in prokaryotes?
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-35
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