Translation Flashcards
mRNA can only be translated if transcripted from
Sense strand
Stop codons
UAA, UGA, UAG
Start codon
AUG
How is a sequence read?
3 possible ways a sequence may be read -> depends on where translation begins. Most mRNA have 1 reading frame because cryptic stop codons.
Types of mutation
Frameshift, mis-sense, nonsense
Aminoacyl- tRNA synthases
Load each tRNA with appropriate amino acid. Each of the 20 recognizes 1 amino acid and all compatible tRNA.
Features of ribosomes in translation
- Synthesize proteins at a rate of 3-5 amino acids/ second
2. Base pair with a codon in the mRNA
2 functions of tRNA
- Covalently link with amino acid
2. Base pair with a codon in the mRNA
Wobble
A single tRNA can recognize more than 1 codon corresponding to a given amino acid. This usually occurs in the 3rd base position of mRNA, leading to multiple pairings which wouldn’t otherwise be possible. e.g. I-U
Initiation of translation
Begins with methionine (AUG), sequences that occur upstream of the first methionine allows cell to know that this is the initiator methionine
Initiation of translation in bacteria
Shine-Dalgarno -> less than 10 bp recognized by ribosome
Initiation of translation in eukaryotes
Kozak sequence -> near 5’end where translation begins mRNA binds to 5’cap
Sub-units of ribosome aren’t joined until
mRNA is present in translation
In elongation,
Peptide bonds are formed causing translocation of tRNA
E,P,A sites
- Exist in both prokaryotes and eukaryotes
- A site crosses both large + small sub-units where codon is recognized
- tRNA translocates to P site
- Next tRNA to E site
