DNA and protein synthesis

• Protein synthesis is the production of proteins

  there are 2 stages

  transcription - where DNA is converted to mRNA

  translation - where the mRNA joins with ribosome and corresponding tRNA molecules bring the specific amino acid the codon codes for
• transcription

  DNA helix unwinds and hydrogen bonds are broken, this forms 2 template strands (only 1 is used), this is catalysed by DNA helicase

  free mRNA nucleotides align opposite the complementary bases on the template strand

  RNA polymerase catalyses the formation of phosphodiester bonds to form pre-mRNA

  splicing removes the introns

  mRNA leaves through nuclear pores into cytoplasm
• Transcription

  in cytoplasm, mRNA attaches to ribosome, the ribosome is attached at start codon

  the tRNA anticodon binds to complementary mRNA codon and held in place by ribosome

  the tRNA brings a specific amino acids

  the ribosome moves along so another tRNA can attach to next codon

  the amino acids are joined by a peptide bond, requires enzyme and ATP

  tRNA released once amino acid has joined

  this continues until stop codon

  polypeptide chain detaches and enters Golgi body for folding
• tRNA molecule

  A - amino acid attachment site

  B - anticodon - complementary to mRNA codon

  The anticodon aligns with complementary codon on mRNA so the tRNA delivers correct amino acid

  
• introns and exons

  introns - non-coding sequences, make up majority of DNA

  exons - coding regions, code for amino acid sequences
• Genome- complete set of genes in a cell

  proteome- full range of proteins a cell is able to produce
• mRNA

  Single-stranded molecule

  uracil bases are present

  significantly shorter than DNA so its able to carry genetic code out of nucleus