Introduction to RNA transcription mRNA processing Flashcards
what is a transcriptosome?
set of all RNA molecules
includes all mRNAs
varies on cell type
what is difference between dna and RNA structure?
hydroxyl group on 2’ C instead of just H
uracil instead of thymine
what does the added hydroxyl group mean?
more reactive than DNA
less stable
catalyst & transient molecule
why does RNA use uracil?
more abundant
avoid cytosine deamination
differences between dna and rna?
rna single stranded
rna form variety of 3D shapes
rna base pair with other nucleic acids
key aspects of RNA synthesis?
synthesised in 5’ to 3’ direction
RNA polymerase
3’ C where new nucleotides added onto
stands run antiparallel
the steps of RNA synthesis
- local unwinding of DNA
- nucleotides bind to template
- formation of phosphodiester bond
- loss of pyrophosphate releasing energy
what is mRNA processing?
processed before it leaves nucleus
premRNA -> mature mRNA
essential for stability
prevents degradation
steps of mRNA processing
- 5’ end capped with atypical nucleotide
- 3’ end tail of poly-A nucleotides
- Intrones removed
what is splicing?
removal of introns
happens as soon as RNA transcribed
removed by spliceosome
spliceosome able to bind to motifs, intron removed
what is alternative splicing?
splicing in different ways to give different isoforms for different cells
i.e. removal of different introns or exons in different ways
selective exporting
RNA binding proteins mark mature mRNA for export from nucleus
facilitate movement out of cell
mRNA degradation
mRNA translated many times
stability determines on how much protein translated
sequence determines its life length