week 7

• Gene


  A gene may determine a characteristic of an individual by specifying a polypeptide chain that forms a protein or part of a protein (structural gene); or by encoding an RNA molecule. A gene may regulate the operation of other genes.
• Central dogma


  1. 5' DNA

  2. 3' DNA

  3. Transcription control regions

  4. Coding region

  5. Protein/RNA
• Types of mutations


  • Small scale: Base substitutions, Frameshift mutations, Triplet repeats
  • Large scale: Deletions, Duplications, Inversions, Insertions, Translocations
• Mutation


  Molecular change that causes a disorder
• Mutation types and disorders

  • Missense: Achrondroplasia
  • Nonsense: Marfan syndrome
  • Insertion: Familial hypercholesterolemia
  • Deletion: Cystic fibrosis
  • Trinucleotide repeat expansions: Huntington disease
• Sample collection


  1. DNA from buccal swab/saliva

  2. Forensic DNA from crime scene

  3. Prenatal: amniocentesis, chorionic villus sampling, cell-free foetal DNA
• Genetic tests


  1. Amino acid deletion - Cystic Fibrosis: Mutant allele migrates faster than wild type in gel electrophoresis

  2. Point mutation - Sickle cell anemia: RFLP analysis

  3. Protein Truncation Test for BRCA2
• Triplet repeats


  Huntington's disease: Autosomal dominant, IT15 gene, huntingtin protein, CAG triplet repeat expansion, late onset, anticipation
• Karyotype


  Chromosomes in cells, 46 chromosomes, 23 pairs, 22 autosomes, 2 sex chromosomes, studied in metaphase