Lecture 24

Question 1

Sxl Early Splicing

Answer 1

initial splicing occurs with E1 exon and the 2 and 3 exons are spliced out thus providing functional proteins

Question 2

RNA Surveillance

Answer 2

MEchanism to deal with errors during RNA processing.
Improperly processed pre-mRNAs are recognized in nucleus and sent to exosome for degradation

Question 3

Incompletely spliced pre-mRNA

Answer 3

remains associated with the spliceosome and is restricted from export

Question 4

Nonsense Mediated Decay

Answer 4

Translational stop codon is normally found in the last exon
NMD targets mRNAs with stop codons that occur before last splice junction
Can occur by errors in splicing causing frameshift
Or a mutation that produces a stop codon or frameshift

Question 5

B thalasemia

Answer 5

BLOOD DISORDER WITH ONE BASE PAIR DELETION this is in the second exon causing a stop codon

Question 6

NMD Mechanism

Answer 6

After splicing EJC is placed at exon exon junction
During export Upf3 stays associated
Ribosomes displace Upf3 during translation pioneer round but cannot be displaced if downstream from a premature stop codon
if Upf3 stays associated, triggers formation of complex that targets degradation

Question 7

Non-stop decay

Answer 7

Targets mRNAs with no stop codon polyadenylation can also cause this

Question 8

NO-go decay

Answer 8

Stalled mRNA gets targeted for degradation because of damage or presence of unusually stable secondary structure

Question 9

Ribosomes

Answer 9

Composed or ribosome and proteins (4 rRNAs for humans and 3 rRNAs for E.coli)

Question 10

Ribosomal Sites

Answer 10

A site (amino acyl) site where new amino acid and tRNA comes in
P site (peptidyl site) site where the tRNA with the peptide is held
E site (exit site) ->tRNA without amino acid sits until kicked off

Question 11

Aminoacyl tRNA synthetase

Answer 11

Recognize and bind to their cognate tRNAs and hydrolyzes ATP to create a high energy ester bond

Question 12

Degenerate genetic code

Answer 12

64 codons and only 20 amino acids
There are more different tRNAs than amino acids and some amino acids can attach to more than one tRNA

Question 13

Wobble pairing

Answer 13

many tRNAs can pair with more than one codon

Question 14

tRNA strucutre

Answer 14

CCA region is where amino acid that gets added.
There is a anticodon loop that binds its corresponding mRNA

Question 15

Wobble position

Answer 15

The first base can be bound to different bases on the third position of mRNA

Question 16

tRNAimet

Answer 16

binds Psite on ribosome unlike all others that bind A site

Question 17

eIF2 ternary complex

Answer 17

eIF2/GTP/Met

Question 18

43S pre initiation complex

Answer 18

eIF2/GTP/Met/eIF1/3/1a/5

Question 19

eIF4E

Answer 19

Binds to mRNA cap structure and then recruits the 43S complex

Question 20

eIF4G

Answer 20

binds eIF3 and poly A tail to stabilize

Question 21

eIF4A

Answer 21

helices that unwinds the mRNA secondary structure

Question 22

eIF4B

Answer 22

enhances eIF4A

Question 23

48S Initiation complex

Answer 23

same as pre initiation but ribosome is at AUG