Transcription in prokaryotes and eukaryotes mRNA modifications -- Lecture 13 Flashcards
template strand and coding strand:
1) RNA polymerase ___, unwinds the DNA strands
binds to the gene
template strand and coding strand:
1) RNA polymerase binds to the gene, ___
unwinds the DNA strands
template strand and coding strand:
1) ___ binds to the gene, unwinds the DNA strands
RNA polymerase
template strand and coding strand:
2) RNA polymerase reads the ___ of the gene
template strand
template strand and coding strand:
2) ___ reads the template strand of the gene
RNA polymerase
template strand and coding strand:
3) the RNA sequence is ___ to the template strand sequence
complementary
template strand and coding strand:
3) the RNA sequence is complementary to the ___
template strand sequence
template strand and coding strand:
3) the ___ is complementary to the template strand sequence
RNA sequence
phases of transcription:
3 phases
initiation
elongation
termination
phases of transcription:
initiation (what happens)
RNA polymerase attaches to the ___ of the gene
attaches to the promoter
phases of transcription:
initiation (what happens)
___ attaches to the promoter region of the gene
RNA polymerase
phases of transcription:
initiation (what does it do)
separates the coding and template strands
phases of transcription:
elongation (what happens)
RNA polymerase ___ the template strand to generate the RNA transcript
transcribes (reads)
phases of transcription:
elongation (what happens)
RNA polymerase transcribes (reads) the ___ to generate the RNA transcript
template strand
phases of transcription:
elongation (what happens)
RNA polymerase transcribes (reads) the template strand to ___
generate the RNA transcript
phases of transcription:
elongation (what happens)
___ transcribes (reads) the template strand to generate the RNA transcript
RNA polymerase
phases of transcription:
termination (what happens):
RNA polymerase reaches the ___ – detaches from the DNA and releases the RNA transcript
termination sequence
phases of transcription:
termination (what happens):
RNA polymerase reaches the termination sequence – detaches ___ and releases the RNA transcript
from the DNA
phases of transcription:
termination (what happens):
RNA polymerase reaches the termination sequence – ___ from the DNA and releases the RNA transcript
detaches
phases of transcription:
termination (what happens):
RNA polymerase reaches the termination sequence – detaches from the DNA and ___ the RNA transcript
releases
phases of transcription:
termination (what happens):
RNA polymerase reaches the termination sequence – detaches from the DNA and releases the ___
RNA transcript
transcription in prokaryotes:
prokaryotes have 1 type of ___
RNA polymerase
transcription in prokaryotes:
___ have 1 type of RNA polymerase
prokaryotes
transcription in prokaryotes:
prokaryotes have ___ of RNA polymerase
1 type
transcription in prokaryotes:
the RNA polymerase has ___ distinct sections
2
transcription in prokaryotes:
2 distinct sections of RNA polymerase
sigma factor
core enzyme
transcription in prokaryotes:
sigma factor (what does it do)
initiates transcription in prokaryotes
transcription in prokaryotes:
core enzyme (what is it and what does it do)
2 alpha, 2 beta subunits
synthesizes the RNA
transcription in prokaryotes:
holoenzyme (what is it)
core enzyme + sigma factor
transcription in prokaryotes:
sigma factor (SF) functions:
SF binds to the promoter regions of genes (DNA sequence recognition)
SF separates the coding and template strands (helicase function)
SF enables the core enzyme to begin transcription
elongation and termination:
the ___ completes transcription w/o the SF
core enzyme
elongation and termination:
once transcription begins:
the SF dissociates from the core enzyme
the SF will then associate w/ another core enzyme and initiate the transcription of another gene
core enzyme completes transcription w/o the SF
transcription/translation in prokaryotes:
in prokaryotes: transcription and translation are ___
coupled
happen at the same time and in the same place w/in cell
transcription/translation in prokaryotes:
why are transcription and translation coupled in prokaryotes?
no nucleus to separate genes and ribosomes
so the mRNA is translated as soon as it’s made
multiple ribosomes translate a single mRNA
polycistronic mRNAS:
in prokaryotes, many RNAs are __
polycistronic
polycistronic mRNAS (definition)
mRNA that contains the coding region of more than one gene
polycistronic mRNAS:
polycistronic mRNAs come from gene clusters called ___
operons
polycistronic mRNAS:
polycistronic mRNAs come from ___ called operons
gene clusters
polycistronic mRNAS:
___ contain sets of genes that work together in a biological function (genes that need to be expressed at the same time)
operons
polycistronic mRNAs:
the genes in an operon are ___ and share ___
transcribed together
share a single promoter region and termination region
example of polycistronic mRNA:
lac operon in prokaryotes
lac operon (definition)
cluster of 3 genes involved in the transport and metabolism of lactose (a carb used for energy)
transcription in eukaryotes:
are transcription/translation coupled in eukaryotes?
no
transcription occurs in nucleus
translation occurs in cytoplasm
transcription in eukaryotes:
___ different RNA polymerases w/ different roles
3
transcription in eukaryotes:
RNA Pol I
transcribes ribosomal RNA genes (rRNAs)
transcription in eukaryotes:
RNA Pol II
transcribes mRNA genes
transcription in eukaryotes:
RNA Pol III
transcribes transfer RNA genes (tRNA) and rRNA genes
transcription initiation in eukaryotes:
do eukaryotic RNA polymerases have a sigma factor?
no
transcription initiation in eukaryotes:
proteins called ___ attach to the promoter region and attract RNA Polymerase
transcription factors
modifications to eukaryotic mRNAs:
in eukaryotes an mRNA is called a ___ until it is modified in 3 important ways
pre-mRNA
modifications to eukaryotic mRNAs:
3 important ways to modify pre-mRNA into mRNA:
1)
a 7-methy-guanosine is added to the 5’ end of the mRNA (5’-cap) (added by capping enzyme)
protects the mRNA from degradation on the 5’ end
modifications to eukaryotic mRNAs:
3 important ways to modify pre-mRNA into mRNA:
2)
addition of a poly-A tail (~200 adenines added to the 3’ end of the mRNA) (added by the enzyme poly-A polymerase)
protects the mRNA from degradation on the 3’ end
modifications to eukaryotic mRNAs:
3 important ways to modify pre-mRNA into mRNA:
3)
next the mRNA will be “spliced”
