Introduction to RNA transcription mRNA processing

Question 1

what is a transcriptosome?

Answer 1

set of all RNA molecules
includes all mRNAs
varies on cell type

Question 2

what is difference between dna and RNA structure?

Answer 2

hydroxyl group on 2’ C instead of just H
uracil instead of thymine

Question 3

what does the added hydroxyl group mean?

Answer 3

more reactive than DNA
less stable
catalyst & transient molecule

Question 4

why does RNA use uracil?

Answer 4

more abundant
avoid cytosine deamination

Question 5

differences between dna and rna?

Answer 5

rna single stranded
rna form variety of 3D shapes
rna base pair with other nucleic acids

Question 6

key aspects of RNA synthesis?

Answer 6

synthesised in 5’ to 3’ direction
RNA polymerase
3’ C where new nucleotides added onto
stands run antiparallel

Question 7

the steps of RNA synthesis

Answer 7

1. local unwinding of DNA
2. nucleotides bind to template
3. formation of phosphodiester bond
4. loss of pyrophosphate releasing energy

Question 8

what is mRNA processing?

Answer 8

processed before it leaves nucleus
premRNA -> mature mRNA

essential for stability
prevents degradation

Question 9

steps of mRNA processing

Answer 9

1. 5’ end capped with atypical nucleotide
2. 3’ end tail of poly-A nucleotides
3. Intrones removed

Question 10

what is splicing?

Answer 10

removal of introns
happens as soon as RNA transcribed
removed by spliceosome
spliceosome able to bind to motifs, intron removed

Question 11

what is alternative splicing?

Answer 11

splicing in different ways to give different isoforms for different cells
i.e. removal of different introns or exons in different ways

Question 12

selective exporting

Answer 12

RNA binding proteins mark mature mRNA for export from nucleus
facilitate movement out of cell

Question 13

mRNA degradation

Answer 13

mRNA translated many times
stability determines on how much protein translated
sequence determines its life length