RNA Processing Review Flashcards Preview

AP Biology 2014 > RNA Processing Review > Flashcards

Flashcards in RNA Processing Review Deck (18):
1

the parts of eukaryotic pre-mRNA (3)

5' untranslated region the coding sequence 3' untranslated region

2

coding sequence

codes for a specific amino acid sequence that will be produced in translation *varies in length depending on the amount of amino acids encoded*

3

3' region

maintains the stability of the mRNA

4

prokaryotic RNA processing

not necessary (aka doesn't happen), because the mRNA is the RNA in prokaryotes and doesn't need to be processed and transcription and translation happen simutaneously (refer to picture)

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5

RNA processing steps

Capping Polyadenylation Splicing

6

Capping

addition of 5' 7-methyl guanosine cap

when the RNA chain reaches around 30 nucleotides long - a guanine group is added to the 5' end of the pre-mRNA

these caps are are recognized by mechanisms in the cytoplasm for translation

the caps keep the RNA safe from degrading by nucleases

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7

Polyadenylation

additiong of poly-A tail at the 3’ end

RNA is cleaved by ribonuclease 

enzyme poly(A) polymerase adds adenine (A) ribonucleotides to the 3' end of the pre-mRNA

*this (A) adenine sequence can be up to 200 bases long!*

 

8

Splicing

removal of introns

introns intervene! they are not expressed in proteins

exons remain in the mRNA sequence and allow for maturity of the mRNA

exons are expressed in proteins

Both exon and intron gene length differs

 

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9

5' Cap Structure 

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10

PolyA Tail

keep the mRNA stable

assist in easy transport of mRNA to cytoplasm

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11

splicosome

intranuclear protein that properly splices mRNA

12

Splice Junctions

the places in which the mRNA is spliced within the boundaries of introns and exons

  • exon GU (5' end of intron) = the splice donor
  • exon AG (3' end of intron) = the splice acceptor
  • Branch site = in the intron, an AT region where there is an adenine (A)

Steps:

  1. Splice donor cleaved
  2. splice donor attaches to branch site and makes a loop structure
  3. splice acceptor is cleaved
  4. intron degrades (because it isn't used) and the splice acceptors are closed

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13

cleave

to split or sever

14

alternative splicing

removal of exons which creates different mRNAs

when a single gene codes for many proteins

different combinations of exons join together and make many different types of mRNA from the pre-mRNA

 

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