Lecture 18: Translation Flashcards
1
Q
What is the triplet codon hypothesis?
A
- Three nucleotides together (codon) gives rise to one amino acid
2
Q
Which codons specify stop?
A
- UAA, UAG, UGA
3
Q
Which codon specifies start?
A
- AUG (also specifies methionine)
4
Q
What happens at methionine?
A
- Translation starts here
5
Q
What is known as the adaptor molecule?
A
- tRNA
6
Q
What are the features of tRNA?
A
- Single strand of RNA
- 70 - 80 nucleotides in length
- At least one tRNA for each amino acid
7
Q
What’re the features of tRNA?
A
- 3 ‘ amino acid attachment site
- 3 nucleotides at bottom = anticodon, interacts with mRNA codon
- Upside down L structure, fits nicely into ribosomes
8
Q
Why are there only 32 tRNAs?
A
- Some tRNAs can recognise more than one codon
9
Q
How is a “charged” tRNA made?
A
- An enzyme recognises the specific amino acid and correct tRNA and joins them together
- There are 20 different enzymes
10
Q
What is translation?
A
- The synthesis of proteins by ribosomes using mRNA
11
Q
What’re the three stages of translation?
A
- Initiation
- Elongation
- Termination
12
Q
What occurs in initiation in eukaryotic cells?
A
- The small ribosomal sub unit and the tRNA binds to the mRNA first
- Then the ribosome comes along
- Energy is required
13
Q
What occurs in elongation in prokaryotic cells?
A
- tRNA carrying amino acid binds to the A site of the ribosome
- Two things happens at the same time:
- Methionine (first amino acid) attaches to amino acid to the right at A site
- Ribosome moves 3 codons along, and amino acid that was at A site is now in the P site, P site —> E site –> leaves
- Repeat process
- Energy is required
14
Q
What occurs in termination of eukaryotic cells?
A
- Release factor (protein) binds to A site in ribosome
- Leads to the dissociation of everything
- Energy is required
15
Q
What is the release factor?
A
- A protein that appears when there’s a stop codon
