Gene Expression: Transcription Flashcards
what is the simplified expression of the central dogma of molecular biology?
dna makes RNA makes protein
transcription is the making of __ from a __ template
RNA; DNA
only ___ (type of RNA) gets translated into protein molecules
mRNA
transcription is catalyzed by a large enzyme common to all life forms ____
rna polymerase
transcription proceeds through 3 steps
- initiation
- elongation
- termination
what happens in initiation of transcription?
RNAP binds to region of DNA called a promoter and the DNA in that region opens up so RNAP can begin transcription
what is a promoter?
a base sequence upstream of the coding portion of a gene containing recognition sites for RNAP to bind
T/F RNAP requires a primer to initiate polymerization.
false
in bacteria, many dna promoters have recognition sites called the -10 and -35 region because ___
they are roughly 10 and 35 nucleotides upstream to the start site
the first nucleotide (start site) of a transcribed DNA sequence (gene) is denoted as ___
+1
T/F RNAP is a multisubunit complex
t
role of alpha subunit
assembly of core enzyme, interacts with regulatory factors
role of the beta subunit
takes part in all stages of catalysis
role of beta 1 subunit
binds to DNA , takes part in catalysis
role of omega (w) subunit
restore denatured polymerase to its native form
role of the sigma 70 subunit
promoter recognition
the entire subunit complex of the RNAP is called the __
holoenzyme
RNAP without the sigma subunit is called the ___
core enzyme
the core enzyme contains the ___
active site
in bacteria, sigma factors recognize and bind ___, targeting ___ to site
promoters; RNAP
core RNAP is capable of carrying out ___, but it cannot ___
transcription; recognize and bind promoter DNA
the holoenzyme RNAP is capable of recognizing and binding ____ and when it does, it forms a ___ complex
promoter dna; transcription complex
the holoenzyme is targeted to the gene promoter by the _-
sigma factor
sigma factors enable recognition of ___
promoter sequence
sigma factors also play a primary role in converting ___ into ___ at the promoter (open-complex formation)
dsdna; Ssdna
T/F most bacteria have multiple sigma factors, all recognizing their own promoter sequence
t
location of transcription in eukaryotes
nucleus
T/F DNA leaves the nucleus in eukaryotes
false
what are the 3 RNA polymerases in eukaryotes and functions?
- RNAP 1: makes rRNA
- RNAP 2: makes mRNA
- RNAP 3: makes tRNA
alpha–Amanitin is made by ____ and inhibits ___
poisonous mushrooms; RNAP 2
which has more subunits, eukaryotic RNAP or bacterial?
eukaryotic
T/F eukaryotic RNAP has a sigma factor
f
in eukaryotes, proteins called called transcription factors bind to ___ and recruit the ___
promoter DNA; RNAP 2
many eukaryotic promoters have a sequence called a ___ that plays the role of a promoter
TATA box
when the TATA is recognized by a TF, allowing other TFs to bind, forming a ___
transcription complex
once made, a transcription complex recruits ___ to form a__
RNAP 2; initiation complex
some TFs allow eukaryotes to control the level of ___
gene expression
some TFs can be activators or repressors: can increase or decrease the likelihood of forming a ___
ignition complex
activator/repressor TFs bind to __ or __ regions upstream of the DNA strand
enhancer; silencer
the ___ of DNA is what allows transcription factors at distant binding sites to work
flexibility
____ catalyses the initiation and elongation of RNA
RNAP
RNAP requires what 3 components?
- a template
- activated precursors
- Mg or Mn cofactor
what is the template for RNAP?
one of the DNA strands
the template strand sequence:
complement of that of the RNA transcript
the coding strand sequence :
same as the RNA transcript, but T in place of U
what are the activated precursors?
the buliding blocks of the RNA product (ribonuclioside triphosphates)
Mg stabilizes ___ and __ on incoming nucleotides
beta and gamma phosphates
after the promoter region, RNAP ___ a 17-bp segment of the DNA double helix so that nucleotides on the template strand can direct the __
unwinds; synthesis of the RNA product
elongation takes place at __ that move along the DNA template
transcription bubbles
what are the 2 main stop singles for transcription in bacteria?
- rho-independent termination
2. rho-dependent termination
what is rho independent termination?
the stop signal is an RNA hairpin (series of bases that form a stable stem and loop) followed by several Us
what is rho-dependent termination?
a rho protein binds the nascent RNA strand and pulls it away from RNA polymerase and DNA template
t/f eukaryotic mRNA is highly processed
true
pre-mRNA acquire a ___ cap and a __ tail and will be spliced by __
guanine 5’ cap’ and poly A 3’tail ; introns
function of guanine cap
prevent deflation and ease translation
function of the poly A tail
prevent degradation and ease translation
poly A polymerase adds about 250 ___ residues to an mRNA after being cleaved after transcription
adenylate
introns can vary between __ and __ nucleotide
50–10 000`
a mixture of __ and __ form small nuclear ribonucleoproteins (snRNPs)
proteins and small nuclear RNA molecules
assembly of 5 snRNPs forms a __
spliceosome
function of spliceosome
catalyze splicing
