Transcription Flashcards
Why is Rna used in transcription?
- it evolved first
- can form many tertiary structures unlike dna (double stranded)
- ribose sugar because -OH group makes it more reactive to phosphate bond breakage
- U instead of T
- mostly non protein coding (only mRNA codes protein)
What is transcription? What direction is RNA synthesis? Using what strand (what direction is that strand on?What strand will the RNA be complementary to and similar to?
Synthesis of RNA from DNA template. RNA synthesis is in 5-3(OH) direction using the template strand which is in the 3-5 directions. So the RNA molecule will be complementary to DNA template and similar to nontemplate (5-3) because U replaces T
Does transcription require a primer?
no
Prok trxn characteristics
- CRISPR (defence mechanism), trxn happens all at once, 1 RNA poly - holoenzyme
Holoenzyme function (a)
assembly of the core
holoenzyme (B)
rNTP binding site
holoenzyme (B’)
binds to DNA template region
holoenzyme (w)
stabilizing of the core
holoenzyme (6)
dictates where RNA poly holo binds to on prok gene at promoter region recognizing the -35 TTGACA and -10 TATAAT (prone to unwind) on the non template strand
where does transcription start?
+1 at A or G
Prok initiation - What binds to the promoter?
What is positioned over the start site and does what producing what?
What determines which strand will be template and direction of transcription?
holo binds to promoter, RNA polly is positioned over start site and unwinds DNA to produce SS template. Consensus sequence on DNA determines which strand will be template and direction of transcription.
Prok Elongation - begins when what is released? What are added? What makes the transcription bubble and what is its ability?
begins when sigma is released, complementary base pairs are added, RNA poly makes transcription bubble with its unwinding and rewinding abilities
Prok Termination - when does transcription stop? Where is the terminator region? What is released? How many termination factore?
trxn stops when RNA reaches terminator region which is upstream of actual termination. Polly is released. 2 termination factors.
Termination factor (1) prok - Rho dependent
poly pauses and dna encodes C rich area and unwinds (helicase activity)
Termination factor (2) prok - Rho independent
inverted repeats and 6-9 A’s following (turn into U’s), RNA polly pauses because the inverted repeats form hairpin separating from template.
Transcription in euk - 3 RNA poly
each recruited to their specific promoter
Transcription in euk - pol 1
rRNA
Transcription in euk - pol 11
mRNA (protein coding)
Transcription in euk - pol 111
tRNA
Transcription in euk - initiation - what complex forms the preinitiation complex containing the TATA box?
TFII (like sigma in prok)
Transcription in euk - elongation - Polly 2 moves along template strand leaving what intact at the promoter?
TF
Transcription in euk - termination polly 1
requires termination factor (like rho factor)
Transcription in euk - termination polly 111 - When does it end?
ends after a string of U’s are transcribed which is a terminator sequence downstream of hair pin (rho independent)
Transcription in euk - termination polly 11
transcription continues past termination sequence. RNA is cleaved at consensus sequence resulting in 2 mRNAs
1 has no protein and the other RAT 1 binds to the 5’ end of the tail and chews us RNA (non coding strand) similar to rho (just does not chew)
Transcription in euk - initiation - Where does the TFIID bind to and what happens?
This TFIID binds at the promoter and polly 11 causes base pairs to unwind
Transcription in euk - initiation - Where is the template strand placed inside?
The template strand is placed inside Pol 11
Transcription in euk - elongation - RNA polly 2 maintains a…?
RNA polly 11 maintains transcription bubble
Transcription in euk - elongation - what is placed over the active site where new nucleotides are added to the 3’ end?
-OH group
Transcription in euk - elongation - what RNA is seperated?
Newly synthesised RNA is separated
