Proteins are synthesized from amino acids through the process of translation
tRNA carries amino acids to ribosome for protein synthesis. Amino acids not involved in decoding - fidelity of protein synthesis requires correct charging of tRNA
Properties of genetic code: triplet(codon), non-overlapping, unambiguous(clear), degenerate, universal
3 phases of translation: initiation, elongation, termination
- tRNA base-pairs with mRNA; wobble base pairing
- mRNA is read from 5' to 3', polypeptide extends from N- to C- terminus
Amino acid on tRNA is not involved in codon recognition
Structure of tRNA
The conformation (three-dimensional shape) of tRNA results from base pairing (hydrogen bonds) within the molecule.
The sequence on 3' end is always CCA: the amino acid attachment site.
Anticodon: site of base pairing with mRNA. Unique for each species of tRNA.
Charging a tRNA molecule
Aminoacyl-tRNA synthetases: for charging a transfer RNA with the correct amino acid
Each enzyme is specific for one amino acid
Properties of genetic code
3 bases made up a codon
Each codon specify one amino acid
Degenerate: more than one codon for the same amino acid
Three phases of translation
- Start codon: AUG
In eukaryotes, ribosome binds to 5' cap and moves along the mRNA to find the first start codon.
- mRNA is read from 5' end to 3' end
- Proteins are synthesized from N-terminus to C-terminus
- Stop codons: UAA, UAG, UGA
Initiation of translation
Elongation of translation
Termination of translation