DNA translation

3/11/25

what is the purpose of translation? steps of translation?

• turning mRNA into protein using tRNA

• occurs in ribosome in cytoplasm

• initiation, elongation, termination

what is tRNA?

• transfer RNA

• vital for bringing amino acids in to form a polypeptide chain

• clover shape due to intermolecular forces that cause it to fold in on itself

• ester bond attaches amino acid on top

• anti-codon at bottom that matches to codon

anti codon vs codon

• codon: 3 base pairs, read in group of 3

• anticodon: opposite bases of codon, matches to codon

how does amino acid attach to tRNA?

• atp and an amino acid are joined in an enzyme 

• tRNA is joined to the amino acid in the enzyme

• forms ‘charged’ tRNA: activated amino acid attached to tRNA through ester bond

ribosome

• site of protein synthesis

• made of ribosomal RNA and proteins

• consist of small ribosome subunit and large ribosomal subunit

• three tRNA sites

• A site: acceptor site

• P site: peptide site, polypeptides formed here

• E site: exit site, tRNA exits ribosome

movement of tRNA through ribosome

• tRNA comes to A site

• anti codon matches to codon

• moves to P site and gives away amino acid to subsequent tRNA

• moves to E site and exits 

initiation of translation

• small subunit recognizes mRNA

• binds to 5’ cap upstream (before) starting codon → met: AUG

• subunit moves 5’ to 3’ until met codon is found

• anticodon UAC recognizes AUG codon

• initiator tRNA enters ribosome, binds directly to P site with met amino acid (no a site)

• large subunit attaches on top to complete ribosome complex

elongation of translation

• complex is ready

• mRNA is read through 

• tRNA comes into A site and has matching anticodon 

• peptide bonds form between P site and A site junction

• tRNA moves to p site, gives amino acid to subsequent tRNA

• polypeptide chain is being built at the top

• tRNA move to E site then leave ribosome

• tRNA in A site moves to P site

• new tRNA enters A site

• continuously moving like factory line

termination of translartion

• stop codon enters ribosome

• no tRNA with anticodon as they do not need to code for amino acids 

• release factor binds instead of tRNA and dismantles complex

• releases polypeptide, free polypeptide

• ribosome breaks apart

wobble hypothesis

• wobble refers to the third spot on the codon

• the third base on the codon is less strict in pairing

• multiple codons code for the same amino acid 

transcribe and translate this template strand of dna and state what is formed after each process

• transcription: 5’ - GUUGCCAAACCU - 3’

• forms mRNA

• translation: Val - Ala - Lys - Pro  

• forms polypeptide chain, one or more fold to become functioning protein

location of transcription vs translation

• transcription occurs inside nucleus

• mRNA leaves nucleus and finds ribosome

• translation occurs in cytoplasm

• builds polypeptide protein 

what are ribosomes made up of?

protein and rRNA (ribosomal RNA)

what happens to polypeptide chain after being fully synthesized?

it travels to the golgi body to undergo folding to be able to carry out a specific function