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18 Cards in this Set
- Front
- Back
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What is the Structure of RNA? What nitrogenous base is in RNA but not in DNA? What is a hairpin?
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DNA (ribose sugar, phosphate group, and nitrogenous base) but the 2' has an OH group instead of just an H
-single stranded but can loop back on itself, forming hairpins uracil instead of thymine (uracil has NO methyl group on 5' carbon) |
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What are the three types of RNA?
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mRNA: messenger RNA, template for protein
rRNA: component of ribosomes tRNA: brings AA to ribosomes to be translated - are specific to each AA |
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What are the 3 RNA polymerases in eukaryotes and what are they used on? How about prokaryotes?
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Polymerase I: transcribes large rRNAs
Polymerase II: trabscribes mRNA Polymerase III: small RNAs (tRNA and 5S rRNA) prokaryotes only have one RNA polymerase |
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Where does RNA transcription take place in eukaryotes? translation?
is a primer required in trascription? why? |
transcription: DNA to RNA in the NUCLEUS
translation: RNA to proteins in the CYTOPLASM NO primer required! |
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How does transcription take place?
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1) opening and winding of DNA double helix
2) one strand of DNA double helix acts as template 3) RNA strand forms but immediately breaks H bond upon rNTP addition, as RNA chain is displaced and DNA double helix reforms |
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What is the DNA template strand? What is the DNA coding strand? What is the primary transcript? How are these all related (base pair sequence wise)?
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DNA template: template of RNA synthesis
DNA coding strand: inactive during RNA synthesis, but will have same sequence the RNA primary transcript RNA primary transcript: the newly synthesized RNA, looks like the CODING strand, except it has U instead of T |
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How does RNA polymerase determine which DNA strand to use as template?
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promoter sequences on DNA
- contiguous (right next to) transcribed region - composed of smaller sequences called "boxes" or "elements" - stablizes polymerase binding |
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How does RNA polymerase control frequency of transcription in eukaryotes?
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position-independent enhancers and silencers from the DNA
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What is the difference between cis-acting and trans-acting?
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cis-acting: on same molecule of DNA near gene being regulated, i.e. promoters
trans-acting: proteins that bind to DNA and influence RNA polymerase |
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What/where is the Pribnow or TATA box?
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In PROKARYOTES, region within promoter at -10, sequence TATAAT
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What is the operator? What can bind here?
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region located between the promoter and the mRNA start point
represors can bind here and inhibit transcription |
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What is a sigma factor? What is an activator? in prokaryotes!!
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required for RNA polymerase to bind the promoter
- there are different sigma factors - released when RNA chain is 10 nt long activators: stimulate transcription by facilitating the binding of the RNA polymerase to the promotor |
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What is a hairpin loop? What is rho factor?
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loop in the transcript (DNA template) that signals for transcription termination
- preceding a number of U residues rho factor is protein that causes release of RNA polymerase |
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What does "polycistronic" mean?
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polycistronic = encodes for more than one protein
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What are the qualities of enhancers?
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- EUKARYOTIC!
- sequences are dissimilar - position independent (can be anywhere in DNA sequence) - orientation independent |
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What are transcription factors (basal factors)?
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bind to TATA box and facilitate binding of RNA polymerase
are not regulated |
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What are activators in prokaryotes?
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communicate with basal factors (transcription factors) via coactivators
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What is the primary transcript (heterogeneous nuclear RNA, hnRNA)? What happens to it?
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- its the original, raw form sequence of transcribed RNA
- undergoes post-transcriptional modification in order to be transported into cytoplasm. these include: - capping of 5' end's phosphates via 5'-5' phosphate linkage - addition of poly (A) tail to 3' end (not encoded in the DNA) makes sure transcript isnt being cut short, adding one A at a time - methylation of some adenosine residues - removal of introns and splicing of exons |
