DNA, RNA & PROTEIN II

• Nutrients


  Things we get from our diet that our bodies need to function
• Chemical digestion


  1. Uses different proteins and enzymes

  2. Breaks down food particles into usable nutrients

  3. Cells can absorb
• DNA


  Contains instructions to manufacture proteins
• Gene


  A continuous string of nucleotides containing a region that codes for an RNA molecule
• Genes


  • Begin with a promoter
  • End in a Terminator
  • Contain regulatory sequences
• Gene expression


  1. Transcription

  2. Translation
• Transcription


  1. DNA used as template to make messenger RNA

  2. Occurs in nucleus

  3. Involves RNA polymerase
• Transcription

  • Initiation
  • Elongation
  • Termination
• Initiation


  Promoter region functions as recognition site for RNA polymerase to bind
• Elongation

  RNA polymerase slides along template DNA strand, adding nucleotides to 3' end of growing RNA molecule
• Termination

  RNA polymerase, DNA strand, and messenger RNA transcript dissociate from each other
• Messenger RNA

  Includes coding exons and non-coding introns
• Intron splicing

  1. Spliceosome removes introns and joins adjacent exons

  2. Produces mature messenger RNA
• Translation


  1. Messenger RNA binds to small ribosomal subunit

  2. Amino acids brought to ribosome by transfer RNA

  3. Peptide bonds form between amino acids

  4. Polypeptide released when stop codon reached
• Codon


  Three-letter code in messenger RNA that specifies an amino acid
• Anticodon


  Sequence on transfer RNA complementary to a codon
• Ribosome


  • Has E, P, and A sites
• Elongation


  Transfer RNA molecule binds to A site, peptide bond forms with amino acid in P site, complex slides one codon to the right
• Release factor


  Binds to A site at stop codon, releases polypeptide from P site
• The purpose of translation is to produce polypeptides quickly and accurately
• Polypeptide modification


  1. Occurs in different organelles

  2. Necessary for protein function
• Proteins are needed for most physiological functions of the body to occur properly