ch 5 Flashcards
Central Dogma of Molecular Biology
DNA used as instructions for RNA
RNA used as instructions for proteins
main steps of trasnscription
- initiation
- elongation
- termination
initiation (transcription)
proteins attach to DNA and open the two strands
transcription factors bind gene at promoter
attracts RNA polymerase
elongation (transcription)
new RNA polymer is produced and extended
termination (transcription)
RNA molecule gets detached and process is over
promotor region
broad term, DNA sequence that shows RNA polymerase where to initiate transcription
contains promoter elements
T/F: different genes have different promoter elements
true
promoter elements
nucleotide sequence that attracts a specific transcription factor
transcription factors ultimately recruit _______
RNA polymerase
how many RNA polymerases do humans have
4
3 in nucleus
1 in mitochondria
function of RNA polymerase
transcribe different gene types
what brings RNA Pol II to promoters
transcription factors called TFIID
TFIID recruits TFIIB
TFIIB recruits RNA Pol II
function of TFIIH
helicase function
opens DNA so transcription can begin
mediator complex
multiple proteins
helps hold everything together
helps release RNA Pol II to begin elongation
pre-initiation complex
full complex of factors necessary to start transcription
all the components in the circle
what causes RNA Pol II to be released
mediator enables RNA Pol II to be phosphorylated
antisense strand
template strand of DNA
RNA is complementary to it
sense strand
other strand of DNA (not template)
RNA is the same as it
what direction does RNA polymerase add nucleotides
5’ to 3’
carboxyl terminal region
long intrinsically disordered trail on RNA polymerase
polyadenylation signal
DNA sequence that initiates termination in transcription
function of carboxyl region on RNA polymerase
platform for other proteins to bind
helps with elongation factors (helps with RNA processing)
termination steps
- Pol II transcribes polyadenylation signal
- signal recruits endonuclease
exonuclease
degrades RNA after polyadenylation signal
during termination of transcription
endonuclease
enzyme that cuts mRNA in transcription
torpedo model
exonuclease runs into and detaches polymerase
during termination of transcription
T/F: new RNAs must undergo maturation/processing
true
precursor RNA
initial RNA before RNA processing
not ready to do its job
mature RNA
RNA after maturation/processing
ready to function
4 main events of processing mRNA
- addition of 5’ cap
- 3’ polyadenylation
- splicing
- editing/modification
RNA capping
inverted guanine added to 5’ end of new RNA
prevents RNA from being degraded by nucleases
3’ polyadenylation
~200 adenines added to 3’ end of mRNA
helps stabilize mRNA
regulate translation
poly-A tail
~200 adenines added to 3’ end of mRNA
RNA splicing
process that removes unnecessary segments
introns
regions that are removed
exons
regions that are retained
how much of the typical human gene is introns
~90%
in mRNAs, only _______ will be translated
exons
alternative splicing
exons spliced together in different combinations
isoforms
different versions of a protein that are produced from the same gene via alternative splicing
Dscam
gene involved in brain function in drosophila
T/F: introns can contain sequences that regulate transcription
true
spliceosome
complex that removes introns
made up of multiple RNA-protein complexes
RNA modification
some nucleotides are chemically modified
another name for RNA modification
post-transcriptional modification
influences RNA functions
RNA degradation
break down of RNA molecules via nucleases
how long does an RNA molecule last in cells
about 12 hours
