Lecture 19: RNA Structure, Transcription, Editing, Transport, Translation
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Is RNA single stranded or double stranded? What kind of shapes does it form?
• single-stranded • makes a variety of 3D shapes
What is conventional base pairing? What is nonconventional base pairing?
Conventional is the typical A:T, G:C type pairing Nonconventional does not follow this pairing, it can be A:G, U:C type pairings
Does RNA use conventional or nonconventional base-pairing?
It uses both
What roles does RNA have a hand in?
Information relay, structural, regulatory, enzymatic roles
Is DNA single or double stranded?
Double stranded
What shape does RNA have? What shape does DNA have?
RNA: variety of 3D shapes DNA: double helix structure
What is the purpose of DNA?
Information storage
Does DNA use conventional or nonconventional base pairing?
Conventional
Why is RNA able to form into a variety of 3D structures?
This characteristic comes from its single-stranded form (similar to how polypeptides fold into unique protein structures)
The fact that RNA can fold into a variety of 3D shapes supports the RNA world hypothesis; what is this hypothesis?
Earliest cells were RNA based before proteins and DNA
What does de novo mean? (in terms of cell bio)
de novo means originating from the beginning without a preexisting template
RNA polymerase catalyzes the synthesis of RNA using what as a template?
One DNA strand
What enzyme catalyzes the synthesis of RNA?
RNA polymerase
What are the substrates used by RNA polymerase in RNA synthesis?
ATP, UTP, GTP, and CTP
What provides the energy for RNA synthesis?
Hydrolysis of high-energy bonds in nucleoside triphosphates (NTPs)
What determined nucleotide selection during RNA synthesis?
Conventional base-pairing rules (A with U, and G with C)
In which direction does RNA polymerase synthesize the RNA strand?
5’ -> 3’ direction
How does RNA polymerase differ from DNA polymerase in starting synthesis?
RNA polymerase can start de novo (without a primer)
What is the function of the active site of polymerase in transcription? See slide 4
It’s where incoming ribonucleoside triphosphates are added to the growing RNA chain
Does newly synthesized RNA remain hydrogen-bonded to the DNA template?
No, it falls off a few base pairs behind where new ribonucleotides are added
What happens to the DNA helix after the RNA transcript falls off?
The DNA helix reforms
Can multiple RNA polymerases use the same DNA template simultaneously? Why?
Yes, because the RNA transcript quickly detaches from the DNA, allowing the DNA helix to reform and remain available for additional polymerases to bind and begin new rounds of transcription
In the grad student iClicker question, why is B correct?
Regulatory system in the cell will only check the most recent base pair bond; since B included G-C after the base pair switch, it’s more likely to be missed by the regulatory system and therefore more likely to succeed
What is the result of multiple RNA polymerases working on the same gene?
Many RNA molecules can be produced from the same gene in a short time