Sets 13 Flashcards
what is a simple explanation of transcription?
RNA copy of DNA gene sequence
in what direction are nucleotides added ?
5’ to 3’
what does RNA polymerase do ?
its an enzyme that catalyzes transcription
what is a promoter ?
a DNA sequence near the start of genes that signal RNA polymerase where to begin transcription
what is a terminators?
sequences in the mRNA that tell RNA pol where to stop
what is the difference between a start codon and a promoter?
a start codon starts the reading frame a promoter help starts transcription before the reading frame
what are the three step of prokaryotic transcription ?
- Initiation
- Elongation
- Termination
what are the 2 things that occur in transcription initiation ?
- Promoter allow RNA pol and sigma factor to bind to begin transcription
- DNA helix open and forms a transcription bubble
in which direction does transcription happen
5’ to 3’
what happens during transcription elongation ?
transcription continues and as the RNA start tailing off the Helix snaps back together
can multiple transcription event occur on 1 DNA strand at the same time
yes as long as the helix snaps back together transcription can go on
what are the two methods of prokaryotic termination?
RHO- dependant & RHO-independant
what is RHO-dependant termination ?
its is when a C rich and G poor sequence calls the RHO protein and it bind and ruins the transcription system and ends up pulling out mRNA from RNA pol
what is RHO-independent termination?
a sequence both C & G rich which cause it to base pair on itself and create a hair pin which makes RNA pol release the mRNA
what are 4 big differences between prokaryotic & Eukaryotic
- addition of 5 end methyl cap
- Addition of 100-200 adenosines to 3’ end (poly-A tail)
3.RNA splicing ; removing introns
4.Exons and introns
what is the methylated cap at the 5’ end of eukaryotes
a reversed GTP with a methyl group attached to guanine
what are the 2 points of the poly-A-tail
to allow transportation to the cytoplasm and allow RNA to live longer in cell
what is RNA splicing ?
removal of introns
how does RNA splicing work ?
at the start of the 5 end of introns enzymes recongnize a sequence which makes it fold on itself halfway and the 3’ end get cut away
what carries out splicing ?
splicesosomes
can RNA transcripts self splice ?
yes
do all eukaryotes contain introns ?
some dont have any and some have alot
