Genetics II

• Central Dogma


  Genes specify the proteins that are made by cells
• DNA replication


  The process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules
• Transcription


  DNA strand is copied into a class of messaging RNA
• Translation


  The RNA instructs protein synthesis
• Mutations


  Changes in the DNA sequence that affects genetic information
• Causes of mutations


  • Mistake during replication
  • Mistake during DNA repair
  • A mutagen
• Where mutations can occur

  • Somatic cells (are not passed to offspring)
  • Gametes (eggs and sperm)
• Gene Mutations


  Change in the nucleotide sequence of the DNA within a gene
• Types of gene mutations

  • Point mutation
  • Frameshift mutation
• Point mutation


  A mutation that changes a single nucleotide in the DNA sequence
• Types of point mutations

  • Synonymous mutation
  • Nonsynonymous mutation
• Transition


  Occurs due to an interchange of purines (A-G) or pyrimidines (C-T) in DNA
• Transversion


  Happens when a purine base is substituted with a pyrimidine base, or a pyrimidine base is substituted with a purine base (C-G) (A-T)
• Effects of point mutations

  • Silent mutation
  • Missense mutation
  • Nonsense mutation
• Frameshift mutation


  Changes the "reading frame" like changing a sentence
• Types of frameshift mutations

  • Insertion
  • Deletion
• Diseases caused by frameshift mutations

  • Cystic Fibrosis
  • Sickle Cell Anemia
• Types of chromosome abnormalities

  • Deletion
  • Inversion
  • Translocation
  • Duplication
• DNA repair mechanisms


  • Direct reversal of mistake
  • Excision repair
• DNA polymerase proofreading


  Backspace button: 3' to 5' exonuclease activity, Re-write new DNA with 5' to 3' polymerase activity
• Photoreactivation


  Fixes UV-induced TT dimers, Light activates photolyase enzyme, Photolyase un-crosslinks TT dimers, Found in bacteria and simple eukaryotes, Not Humans