BIO 205 RNA PROCESSING

Question 1

simultaneous transcriptions and translation… where?

Answer 1

only in prokaryotes

Question 2

no significant mRNA processing in __

Answer 2

prokaryotes

Question 3

Processing of eukaryotic messenger RNAs

Answer 3

1. 5’ processing (5’ cap)
2. 3’ processing (poly-A tail)
3. intron removal (splicing of exons)

Question 4

UTRs

Answer 4

untranslated regions at the 5’ and 3’ ends

Question 5

5’ UTR function

Answer 5

ribosomal binding site

Question 6

3’ UTR function

Answer 6

signal for polyadenylation (Poly-A)

Question 7

5’ modification (5’ cap)

added WHEN

Answer 7

shortly after transcription when mRNA is ~20-30 nts

Question 8

functions of 5’ Cap in Eukaryotic mRNA

Answer 8

• protects mRNA from 5’ exonucleases (Stability)
• helps transport mRNA to cytoplasm
• necessary for ribosome binding in translation

Question 9

3’ cap (poly-A tail addition) process

Answer 9

• Polymerase II continues to synthesize mRNA into 3’UTR region
• polyA polymerase recognizes the sequence and add string of As

Question 10

poly-A tail addition stands for

Answer 10

polyadenylation

Question 11

Functions of 3’ poly-A tail addition in eukaryotic mRNA

Answer 11

• protects mRNA from 3’ exonucleases (Stability)
• helps transport mRNA to cytoplasm
• will get chewed up, but UNIMPORTANT

Question 12

exonucleases

Answer 12

enzyme which removes successive nucleotides from the end of a polynucleotide molecule

Question 13

exons and introns aka

Answer 13

exons: coding regions
introns: noncoding

Question 14

5’ cap formation

Answer 14

7-methylguanosine 
-------
5'-to-5' triphosphate bridge
-------
5' end of primary transcript

Question 15

R-Looping Experiments

in vitro

Answer 15

1. Denature double strand DNA
   - big loop
2. anneal (recombine) single-strand DNA + RNA from same gene
   - double-stranded DNA is now INTRON in between 2 r-loops
3. Observe DNA-RNA hybrids under microscope

Question 16

why must splicing occur precisely

Answer 16

to prevent deleterious translational defects

Question 17

Splicing disorder (non-precise)

Answer 17

thalassemia

Question 18

splicing needed

Answer 18

to make transcript

Question 19

sequences required for intron removal

Answer 19

EXON 1: —AG
BRANCH SITE: “A”
EXON 2: G—

Question 20

EXON 1 must:

Answer 20

end in —-AG

Question 21

EXON 2 must:

Answer 21

start w G—

Question 22

BRANCH SITE must:

Answer 22

have an “A”

Question 23

WHY DOES SPLICING OCCUR

Answer 23

BECAUSE INTRONS ARE NONCODING (IRRELEVANT) AND NOT-NEEDED

Question 24

branch point sequence

Answer 24

connects introns together - forming lariat

Question 25

lariat

Answer 25

only intron sequencing

Question 26

linkage of splicing

Answer 26

5’ –> 2’

Question 27

spliceosome complex

Answer 27

• consists of small nuclear RNAs (snRNAs) and proteins (U’s)

* form small nuclear ribonucleoprotein particles —–(snRNPs or “snurps”)

Question 28

snRNPs

Answer 28

small nuclear ribonucleoprotein particles

Question 29

what does spliceosome complex DO

Answer 29

• mediates RNA splicing
• specific base-pairing
between snRNA (of SNURP) and mRNA directs splicing process

Question 30

Gene Splicing Mechanism

Answer 30

• intron sequence has 2 exons on end
• 2’ OH from BRANCH SITE loops to bind to exon 1
• exon 1 removes itself, moving to bind to exon 2
• excised intron sequence forms LARIAT
• 5’ —> 2’ linkage
• 3’ end: -OH coming off lariat
• remaining:
- lariat & portion of spliced pre-mRNA

Question 31

when does gene splicing occur

Answer 31

after mRNA is formed from transcription

Question 32

alternative splicing used when

Answer 32

to produce various mRNAs

Question 33

alternative splicing:
-exon1—exon2—exon3-
REMAINS

Answer 33

1-2-3
2-3
1-2

Question 34

Alpha-Tropomyosin gene

Answer 34

• alternative splicing

* multiple proteins possible from one gene

Question 35

end of RNA processing…

Answer 35

mRNA now mature