Lecture 2 pt 2 Flashcards
what is the major enzyme involved in transcription
RNA polymerase
what is the major enzyme involved in DNA replication
DNA polymerase
what direction is RNA synthesized from
5’ to 3’
what direction is DNA synthesized from
5’ to 3’
true/false RNA is synthesized from an RNA template
- false
- a DNA template
RNA polymerase catalyzes the formation of what kind of bond
phosphodiester bond
DNA polymerase catalyzes the formation of what kind of bond
phosphodiester bond
DNA polymerase catalyzes the formation of what kind of phosphodiester bond from linkage of what
deoxyribonucleotides (dNTPs)
RNA polymerase catalyzes the formation of what kind of phosphodiester bond from linkage of what
ribonucleotides (rNTPs)
does RNA polymerase require a primer to initiate synthesis
no
does DNA polymerase require a primer to initiate synthesis
yes (either DNA or RNA)
RNA polymerase has a _____ proofreading mechanism
- modest
- error of 1/10^4
DNA polymerase has a _____ proofreading mechanism
- good
- error of 1/10^7
why is there a difference in proofreading abilities
- cause DNA is the main copy
- RNA is transient and based off DNA
- if you do RNA wrong, just do it again it doesn’t matter
what composes a holoenzyme
the core AND the sigma
what does the sigma factor do
enables holoenzyme to bind selectively to diff promotor sequences
how many types of core enzymes are there
one type (not one molecule… one type)
how many types of σ factors are there
several
why are diff σ used by the enzyme
to recognize diff promotors
what is a promotor
a region that tells the RNA pol where to sit on the DNA to start transcription
describe the transcription cycle of bacterial RNA pol
- initiation starts
- σ factor and core subunit of RNA pol associate to form holoenzyme
- holoenzyme slides along DNA
- σ factor recognizes promotor sequence on DNA
- closed complex forms at promotor
- open complex now forms, aka transcription bubble
- abortive initiation happens, aka scrunching. instead of moving along the DNA, the pol stands there and brings the strand towards itself
- promotor clearance, breaks free from the promotor, and σ is released
- elongation starts
- elongation happens idk thats a later thing
- termination starts
- RNA pol reaches and transcribes termination sequence on template DNA
- a hairpin will form on the RNA
- this causes the RNA pol to release its hold on the RNA
what is the yellow part
coding sequence
what is the part to the left of the yellow
upstream
what is the part to the right of the yellow
downstream
what part will be transcribed
what is the red part
consensus sequence of the promotor
what part will be translated
true/false initiation of transcription occurs at the ATG start codon
false
true/false diff promotors are recognized by diff types of sigma factors of RNA polymerase
true
what does UTR stand for
untranslated region
what are the 2 ends
- amino
- carboxyl
what decides how much RNA is made
promotor
which gene has high and low expression
true/false promotor sequences are often symmetrical to ease binding options
- false
- asymmetrical so RNA pol can bind in one orientation only
when is the bottom DNA strand the template
if youre going from left to right
when is the top DNA strand the template
going from right to left
each type of eukaryotic RNA pol contains how many subunits
at least 10
what does RNA pol I transcribe
- 5.8S rRNA
- 18S rRNA
- 28S rRNA
what is alpha amanitin
- a compound in a poisonous mushroom
- diff RNA pols have diff sensitivity to it
what does RNA pol II transcribe
- mRNAs
- snoRNA
- miRNA
- siRNA
- lncRNA
- most snRNA
what does RNA pol III transcribe
- tRNA
- 5s rRNA
- some snRNA
- other small rRNA
how sensitive to alpha-amanitin is RNA pol I
insensitive
how sensitive to alpha-amanitin is RNA pol II
very sensitive
how sensitive to alpha-amanitin is RNA pol III
moderately sensitive
how can we use RNA pol sensitivities to alpha-amanitin in lab
you can put a tiny bit of poison (alpha amanitin) into your sample in the lab to determine which RNA polymerase is being used
eukaryotic RNA pol require what before they bind selectively to diff promotor sequences
the presence of additional initiation proteins (transcription fators)
rank the diff RNA pol sensitivities to alpha-amanitin
- most
- pol II
- pol III
- pol I
what is often the first transcription factor to bind
TATA binding protein (TBP)
the transcriptional start site is usually indicated by what
a +1 arrow
what transcription factor has helicase activity
TFIH
