Chapter 12: Molecular Genetics

• DNA


  A double helix comprising two strands of nucleotides, each nucleotide formed of a sugar, a phosphate group and one of four different bases
• Chromosome


  A molecule of DNA wrapped around proteins to form a single chromatin thread, which coils more tightly during cell division to form chromosomes in the cell nucleus
• Gene


  A segment of DNA, made of a sequence of nucleotides, which controls the production of a particular polypeptide and is a unit of inheritance located on a locus of a chromosome

  
• DNA


  • Instructions to build a living thing found in the nucleus
  • Too long, coiled up and placed in 46 boxes called chromosomes
• From DNA to protein

  1. DNA -> chromatin -> chromosome

  2. DNA -> mRNA -> polypeptide -> folded protein

  
• Adenine binds to thymine and cytosine binds to guanine by hydrogen bonds in the double helix structure
• Genes control the production of polypeptides (proteins) and are inherited from parents to offspring
• Producing human insulin in bacteria


  1. Identify insulin-producing gene in human chromosome

  2. Cut gene using restriction enzyme to produce 'sticky ends'

  3. Obtain plasmid from bacterium and cut with same enzyme

  4. Mix plasmid and DNA fragment, add DNA ligase to form recombinant plasmid

  5. Mix recombinant plasmid with E.Coli, apply heat/electric shock for entry

  6. Culture E.Coli in fermenter, harvest insulin protein
• Genetic engineering


  Possible benefits and ethical considerations in medicine and production of economically important plants and animals