RNA structure and Transcription Flashcards
By what process is RNA made?
DNA is copied into RNA by a polymerisation reaction known as TRANSCRIPTION
How are RNA turned into proteins?
RNA transcripts can be decoded to generate proteins through translation
What is RNA?
A linear polymer of nucleotides.
Nucleotides are building blocks
How does transcription start and end?
it starts at the Promoter region on a DNA strand and ends at a Terminator region.
How does the stucture of DNA and RNA differ?
Strands:
DNA: Double-stranded (double helix)
RNA: Single-stranded
Sugar:
DNA: Deoxyribose
RNA: Ribose
Bases:
DNA: Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
RNA: Adenine (A), Uracil (U), Cytosine (C), Guanine (G)
Length:
DNA: Longer (can be several centimeters)
RNA: Shorter (usually a few thousand base pairs)
Location:
DNA: Mostly in the nucleus (also in mitochondria)
RNA: Formed in the nucleus, functions in the cytoplasm
What the “A minor motif”?
its an example of tertiary interaction in RNA
it consists of 2 adjacent A residues that interact with the edge of a G:C base pair.
What is an element of the secondary structure of RNA?
Stem loops structures
What is RNA essential for?
It is essential for bringing the genetic information from DNA into cells, where it can be used
What are the base pairs within RNA?
Thymine is replaced by uracil
Guanine - cytosine
Adenine - uracil
What is mRNA?
Messenger RNA
(Takes info out the nucleus to where it can be used to make proteins)
What are cellular RNA’s made by?
RNA polymerases (RNAP)
What is RNA transcript?
The RNA molecule that is produced when a gene is transcribed from DNA. It’s the initial RNA product before any potential processing
The RNA transcript has the same structure as what?
The coding strand on DNA (except that U’s are found in place of T’s)
describe the process of transcription
Initiation- RNA polymerase attached to the promoter region on the template strand of DNA at the beginning of the gene it wants to copy
Elongation- RNA polymerase runs down the DNA template strand reading the bases and bringing in the new RNA nucleotides with the proper complementary bases. As the polymerase runs down the DNA, it unwinds the DNA.
Termination- RNA polymerase continues adding nucleotides until it reaches a specific DNA sequence called the terminator. Upon reaching the terminator, RNA polymerase releases both the DNA template and the newly synthesized mRNA molecule.
what are the 3 nuclear RNA polymerases in eukaryotic cells?
rRNA (RNA polymerase I)
mRNA (RNA polymerase II)
tRNA (RNA polymerase III)
What are the components of E. coli RNA polymerase?
2 α subunits
β and β’ subunits
ω subunit
what are the similarities and differences of transcription in proks and euks?
Similarities
- Template: Both use DNA as the template for RNA synthesis1.
- Product: Both produce RNA molecules1.
- Enzyme: RNA polymerase facilitates transcription in both1.
- Chemical Composition: The chemical composition of the RNA transcript is similar in both1.
Differences
- Location:
- Prokaryotes: Transcription occurs in the cytoplasm2.
- Eukaryotes: Transcription occurs in the nucleus.
- RNA Polymerase:
- Prokaryotes: One type of RNA polymerase synthesizes all types of RNA1 and they have sigma factors.
- Eukaryotes: Three types of RNA polymerase (I, II, III) synthesize different types of RNA1, and they don’t have sigma factors.
- Transcription and Translation:
- Prokaryotes: Transcription and translation occur simultaneously.
- Eukaryotes: Transcription and translation are separate processes; transcription occurs in the nucleus and translation in the cytoplasm.
- Initiation:
- Prokaryotes: Simple initiation machinery with a sigma factor.
- Eukaryotes: Complex initiation machinery with multiple transcription factors.
- RNA Processing:
- Prokaryotes: RNA is often ready for translation immediately after transcription.
- Eukaryotes: RNA undergoes extensive processing (capping, polyadenylation, splicing) before translation
what is a sigma factor? why is it needed in prokaryotic transcription?
Sigma factors are essential for accurate initiation of transcription in prokaryotes.
They provide specificity by directing RNA polymerase to the correct promoter sequences.
*They guide RNA polymerase to the correct starting points of genes on DNA.
Do eukaryotic cells express sigma factors?
No
As we know, eukaryotic cells do not need sigma factors for initiation of transcription. So what do factor do they require for the assembly of RNAP II onto the promoter?
gTF (such as TFIIA or TFIIB)
