Gene Products And Protein Synthesis

Question 1

How many codons code for 20 aa? What does this say about the code?

Answer 1

64

Degenerate

Question 2

Types of point mutations, their consequences

Answer 2

Silent: same aa
Missense: different aa
Nonsense: stop codon

Question 3

Types of frame shift mutations, consequences

Answer 3

Insertion
Deletion

Completely different sequence of aa produced

Question 4

Trna structure

Answer 4

75-90 nucleotides 
Internal base pairing-> cloverleaf structure 
Weird bases
Anticodon on central loop
CCA-OH at 3’

Question 5

Wobble mechanism

Answer 5

Last base on anticodon forms non-Watson crick bp-> tRNA recognises >1 codon

Question 6

How’re aas activated, what’re the called pre/post activation

Answer 6

Aas loaded using aminoacyl-tRNA-synthethases

Aa+trna +atp -> aminoacyltrna + ppi + amp

Trnaphe-> phe-trnaphe

Question 7

Composition of 70S subunit

Answer 7

Large subunit (50S): 23S rRNA + 5S rRNA + 34 proteins
Small subunit (30S): 16S rRNA + 21 proteins

Question 8

Things needed for Initiation

Answer 8

Initiation complex: mrna + ribosome + formylmethionine-trna fmet
Initiation factor : if 1/2(activated by binding to GTP) /3

Question 9

Process of initiation

Answer 9

IF 1&3 bind to 30S 
Mrna binds through E site
Fmet-tRNA-fmet binds to GTP-IF2 and enters P site 
Anticodon lines up with AUG 
50S subunit binds -> GDP + pi released

Question 10

What’s the shine dalgarno sequence

Answer 10

Sequence is upstream of AUG, binds to 16S rRNA

Ensures in-frame translation

Question 11

Process of elongation

Answer 11

Activated aa binds to EF-Tu GTP and enters A site
Proof reading occurs and GTP Is hydrolysed
EF-tu GDP is released
Peptidyl transferase forms peptide bonds between aa
EF-G-GTP binds, GTP hydrolysis-> translocation

Question 12

Termination process

Answer 12

Stop codon at A site 
Release factor 1&2 bind 
Hydrolysis of protein from trna 
Trna translocates to E
Disassembly of ribosome (requires IF3+ ribosomal recycling factor+ GTP HYDROLYSIS)

Question 13

Stop codons

Answer 13

UAG
UGA
UAA

Question 14

How is eukaryotic hnrna modified before being exported out of nucleus

Answer 14

5’ cap
Poly A tail
Splicing

Question 15

Targets of different antibiotics

Answer 15

1. Cell membrane
2. Cell wall synthesis
3. Folic acid synthesis
4. DNA gyrase
5. RNA polymerase
6. 30S ribosome inhibitors eg tetracycline
7. 50S ribosome inhibitors eg chloramphenicol/erythromycin