Protein Synthesis

• Process that makes proteins• Occurs in nucleus and ribosome• 2 Parts: Transcription and Translation

DNA mRNA tRNA A – T A – U A – U T – A T – A U – A

C – G C – G C – G G – C G - C G – C

Steps of Transcription1) RNA polymerase binds to DNA at a specific sequence of

nucleotides called the promoter2) RNA polymerase than unwinds DNA at the beginning of the

gene– Only one DNA strands acts as a template

3) Free RNA nucleotides pair up with their complementary bases on the exposed DNA template

4) RNA polymerase continues until it reaches the terminator sequence

Transcription stops and mRNA polymerase and the new mRNA transcript are released from DNA

• DNA double helix reforms• mRNA leaves and goes to the ribosome

Transcription

Steps of Translation1) Initiation begins with rRNA reading the start codon AUG

Codon – series of 3 nitrogen bases on mRNA (how it’s read)

2) The tRNA with the anticodon UAC will bound to the codon AUG, bringing the amino acid methionine

Anticodon – series of 3 tRNA bases that match a mRNA codon

3) The ribosome slides down to the next codon4) tRNA brings the next amino acid based on its anticodon matching the next

mRNA codon5) A peptide bond forms between the two amino acids

Translation ends when one of three stop codons UAA, UAG, or UGA is reached• The polypeptide chain is released; protein is complete

Translation