RNA Processing Review

Question 1

the parts of eukaryotic pre-mRNA (3)

Answer 1

5’ untranslated region the coding sequence 3’ untranslated region

Question 2

coding sequence

Answer 2

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

Question 3

3’ region

Answer 3

maintains the stability of the mRNA

Question 4

prokaryotic RNA processing

Answer 4

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)

Question 5

RNA processing steps

Answer 5

Capping Polyadenylation Splicing

Question 6

Capping

Answer 6

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

Question 7

Polyadenylation

Answer 7

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!*

Question 8

Splicing

Answer 8

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

Question 9

5’ Cap Structure

Answer 9

Question 10

PolyA Tail

Answer 10

keep the mRNA stable

assist in easy transport of mRNA to cytoplasm

Question 11

splicosome

Answer 11

intranuclear protein that properly splices mRNA

Question 12

Splice Junctions

Answer 12

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

Question 13

cleave

Answer 13

to split or sever

Question 14

alternative splicing

Answer 14

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