BIO 2306 Exam 3
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46 Terms
what is transcription
the process of copying DNA into RNA using RNA polymerase
What’s the function of a poly-A tail
stabilizes mRNA by protecting it from degradation and allowing it to remain in the cell longer for translation
What is the template strand
DNA strand used to build RNA
What is a consensus sequence
a common DNA sequence found in many promoters that helps proteins bind
What happens if a promoter sequence is mutated
transcription is reduced or does not occur
What is the coding (non-template) strand
The DNA strand that has the same sequence as the RNA strand except T → U
What are the main parts of protein-coding gene expression
promotor, coding region, terminator
What are the three stages of transcription
initiation, elongation, and termination
What direction is RNA synthesized
5’ → 3’
What is a bacterial promoter
a DNA sequence where RNA polymerase binds to start transcription
What are the two key promoter regions in bacteria
-10 region (Pribnow box)
-35 region
what is the role of the sigma factor in prokaryotes
helps RNA polymerase recognize and bind to the promoter
What happens after RNA polymerase binds to the promoter
DNA unwinds so that RNA polymerase can use the template strand to make the RNA strand
what happens during elongation
RNA polmerase moves along DNA and builds RNA
What is rho-independent termination
RNA forms a hairpin loop which causes RNA polymerase to stop in prokaryotes
What is rho-dependent termination
A protein called rho binds RNA and pulls it off the DNA
Which RNA polymerase makes mRNA
RNA polymerase II in eukaryote
What is the eukaryotic promotor
DNA sequence where transcription begins, includes TATA box
What is TATA box
a promoter sequence that helps position RNA polymerase in eukaryote
What are general transcription factors
protein that helps RNA polymerase bind and start transcription in prokaryotes
what is the transcription initiation complex (eukaryotes)
RNA polymerase + transcription factors at the promoter
what is pre-mRNA
the initial RNA transcript before modification
What are the three major RNA modefications
5’ cap, 3’ poly-A tail, and splicing
What is the 5’ cap
a modified 7-methylguanosine added to the start mRNA
function of 5’ cap
protects RNA and helps ribosome binding
What is the poly-A tail
A string of adenines added to the 3’ end
difference between core enzyme and holoenzyme
core enzyme has only the RNA polymerase alone while the holoenzyme has the RNA polymerase and the sigma factor
what is a transcription bubble
region where DNA is unwound during transcription
what do topoisomerases do in transcription
relieve supercoiling stress
does proof reading occur in transcription
yes, but less accurate than DNA replication
What RNA polymerase makes mRNA in eukaryotes
RNA polymerase II
What is TBP
TATA-binding protein that binds the TATA box
what is the preinitiation complex
RNA polymerase II + transcription factors at the promotor
What does TFIIH do in eukaryotes
unwinds DNA + activates RNA polymerase II
what are enhancers
DNA sequence that increase transcription
what is the mediator complex
links transcription factors to RNA polymerase II
What is a 3’ cleavage site
Where RNA is cut before adding poly-A tail
What is Rat1
Exonuclease that helps terminate transcription
What are introns
non-coding regions removed
what are exons
coding regions kept
what is alternative splicing
one gene → multiple proteins
what is the spliceosome
complex that removes introns
What is translation
mRNA → protein
what is a codon
3 nucleotides coding for an amino acid
what is the start codon
AUG
what are stop codons
UAA,