L21 Translation Flashcards
In translation mRNA is used as a template for the…
Production of a polypeptide
Three 3 key characteristics of the genetic code are…
- Triplet code
- Non-overlapping
- Degenerate (redundant)
The genetic code is degenerate, which means one amino acid can be encoded…
By more than one codon
Different codons which code for the same amino acid are known as…
Synonymous codons
61 codons specify…
Amino acids
3 codons specify…
Stop
The stop codons are…
UAA, UAG, UGA
AUG codes for which amino acid?
Methionine
The start codon is…
AUG (methionine)
The code for amino acids:
a) varies between species
b) is almost universal
c) is universal
d) varies between prokaryotes and eukaryotes
b) is almost universal
There are a few exceptions, for example the stop codon in mitochondria, UGA codes for tryptophan
The ‘t’ in tRNA stands for…
Transfer
tRNAs form the link between…
RNA and protein
The primary structure of tRNAs (4)…
- Small (70-90nts)
- 15 invariant residues & 8 semi invariant residues
- 5’ monophosphate
- Modified bases (added post-transcription)
The modified bases in tRNA are (4)…
- Ribothymidine (T)
- Pseudouridine (Ψ)
- Dihydrouridine (D)
- Inosine (I) *
*important
The secondary structure of tRNAs (5)…
- D loop
- I Loop
- Variable arm
- Anti-codon loop *
- Amino Acid acceptor site *
*important
Adding amino acids to tRNA is known as the…
Aminoacylation of tRNA
Aminoacylation of tRNA results in…
Charged (aminoacyl) tRNAs
Aminoacylation of tRNA is a ( 1 / 2 / 3+) step reaction…
2
Aminoacylation of tRNAs:
a) Does not require additional energy
b) Is driven by GTP
c) Is driven by ATP
d) Is driven by ADP
c) Is driven by ATP
Aminoacylation step 1 forms a high energy intermediate known as…
Aminoacyl Adenylate (AMP + Amino Acid)
Two free phosphates are released from the original ATP
In step 2 of aminoacylation, the aminoacyl adenylate reacts with…
A matching tRNA
This forms the aminoacyl tRNA and releases the AMP
Amino acids are joined to either the 2’ or 3’ hydroxyls. This doesn’t matter because…
The two forms can freely interconvert
Aminoacylation of tRNA involves the enzyme…
Aminoacyl tRNA synthetase (clases I and II)
Aminoacyl tRNA synthetase recognises tRNAs based on their…
Identity elements
What mechanism allows the aminoacyl tRNA synthetase to differentiate between similar amino acids?
Double-sieve mechanism
The double-sieve mechanism involves the acylation site and the editing site, ensuring the amino acid is neither…
Too large or too small
serine tRNA is written as…
tRNA^ser
where ‘ser’ is superscript
serine is joined to tRNA^ser by…
Seryl-tRNA synthetase
serine + tRNA^ser forms…
ser-tRNA^ser
also known as seryl-tRNA^ser
The number of tRNA types is:
a) equal to the number of codons
b) more than the number of codons
c) less than the number of codons
c) less than the number of codons
Some tRNAs can recognise multiple codons through…
Wobble base pairing
In wobble base pairing the 5’ base on the tRNA anticodon forms…
Non-standard base pairs
e.g. G - U , I - A, I - C, I - U
The difference between class I and class II aminoacyl tRNA synthetases is that they bind…
To different faces of tRNA
What are the major feature of tRNA molecules and what are their functions (2)…
- Anticodon loop (allows binding to matching mRNA codons)
2. Amino acid acceptor site (binds specific amino acid)
