Translation: mRNA binds to ribosome and translates into polypeptide chain
● tRNAs (transport RNA) mediate translation of mRNA codons to amino acids
○ tRNA are short single-stranded
○ tRNA anticodon base pairs with mRNA codon
○ tRNA brings the correct amino acid based on the codons
● Three levels of tRNA structure
○ Primary structure: sequence of nucleotides
○ Secondary structure: short complementary sequences within tRNA that fold on
itself (cloverleaf shape)
○ Tertiary structure: formed by additional folding (L shape)
■ In tertiary structure, an anticodon binds to mRNA codon (complementary)
● aminoacyl-tRNA synthetases catalyze attachment of tRNA to amino acids
○ Binds correct amino acid using atp to 3’ end of tRNA
■ Hydroxyl group of 3’ end on
tRNA binds to carboxyl group of
amino acid
● Wobble: some tRNAs recognize more than one
codon
● Translation
○ Ribosome: combination of RNA
molecules and proteins
■ rRNA: Large subunit and small
subunit
● Different parts of a ribosome
○ Large subunit
■ Aminoacyl (A) site
■ Peptidyl (P) site
■ Exit (E) Site
○ Peptidyl transferase: binds new amino acid onto growing
polypeptide (on top of ribosome)
■ Small subunits bind to mRNA
■ Large subunit has peptidyl transferase activity
● Initiation of translation
○ Prokaryotes: need a special sequence on mRNA (shine-dalgarno box), ribosome
binding site, so ribosome can recognize where it’s supposed to bind
■ fMet (start codon, special methionine) positioned in P site and large
subunit binds
■ Dont have introns, doesn’t need additional processing
○ Eukaryotes: mature mRNA are processed (5’ cap) where small subunit binds and
moves along mRNA until start codon
● Elongation of translation
● tRNAs (transport RNA) mediate translation of mRNA codons to amino acids
○ tRNA are short single-stranded
○ tRNA anticodon base pairs with mRNA codon
○ tRNA brings the correct amino acid based on the codons
● Three levels of tRNA structure
○ Primary structure: sequence of nucleotides
○ Secondary structure: short complementary sequences within tRNA that fold on
itself (cloverleaf shape)
○ Tertiary structure: formed by additional folding (L shape)
■ In tertiary structure, an anticodon binds to mRNA codon (complementary)
● aminoacyl-tRNA synthetases catalyze attachment of tRNA to amino acids
○ Binds correct amino acid using atp to 3’ end of tRNA
■ Hydroxyl group of 3’ end on
tRNA binds to carboxyl group of
amino acid
● Wobble: some tRNAs recognize more than one
codon
● Translation
○ Ribosome: combination of RNA
molecules and proteins
■ rRNA: Large subunit and small
subunit
● Different parts of a ribosome
○ Large subunit
■ Aminoacyl (A) site
■ Peptidyl (P) site
■ Exit (E) Site
○ Peptidyl transferase: binds new amino acid onto growing
polypeptide (on top of ribosome)
■ Small subunits bind to mRNA
■ Large subunit has peptidyl transferase activity
● Initiation of translation
○ Prokaryotes: need a special sequence on mRNA (shine-dalgarno box), ribosome
binding site, so ribosome can recognize where it’s supposed to bind
■ fMet (start codon, special methionine) positioned in P site and large
subunit binds
■ Dont have introns, doesn’t need additional processing
○ Eukaryotes: mature mRNA are processed (5’ cap) where small subunit binds and
moves along mRNA until start codon
● Elongation of translation
