molecular genetics

• Nitrogenous bases


  • Adenine
  • Thymine
  • Cytosine
  • Guanine
• Structure of DNA molecule

  1. Basic unit is a nucleotide, consisting of deoxyribose sugar, phosphate group, nitrogenous base

  2. Four nitrogenous bases: Adenine, Thymine, Cytosine, Guanine

  3. Nitrogenous bases form complementary base pairs: A-T, C-G

  4. DNA molecule is made of anti-parallel polynucleotide chains held together by hydrogen bonds, forming a double helix
• Gene


  Unit of inheritance, small segment of DNA containing sequence of nucleotides which codes for a particular trait
• Chromosome


  DNA or genetic material coiled with proteins to form chromosomes when cell is preparing for cell division
• Codon


  Three bases form a codon in a gene, each codon codes for one amino acid
• Requirements of Genetic Engineering

  • Gene of interest
  • Restriction enzyme
  • Vector (from plasmid)
  • DNA ligase
• How a polypeptide/protein is made

  1. Message in gene copied into mRNA

  2. mRNA travels from nucleus to cytoplasm

  3. mRNA attaches to ribosome

  4. Ribosome moves along mRNA synthesizing polypeptide

  5. Polypeptide released when ribosome leaves mRNA
• Transgenic organism


  An organism that obtains a foreign gene from other organisms of same or different species, generated artificially
• Genetic engineering is a technique to transfer genes from one species to another species
• Procedure for genetically engineering bacteria to produce human insulin

  1. Obtain DNA segment with insulin gene

  2. Obtain plasmid, cut with same restriction enzyme

  3. Mix plasmid and insulin DNA, bind by complementary base pairing

  4. Add DNA ligase to seal insulin gene into plasmid (recombinant plasmid)

  5. Mix recombinant plasmid with E.coli, apply heat shock to allow entry

  6. Isolate and grow transgenic bacteria in fermenter, extract and purify insulin
• Benefits of Genetic Engineering

  • Mass production of insulin
  • Production of crops that grow in extreme conditions
  • Reduced cost of drugs
  • Allowing farmers to grow crops in unsuitable conditions
  • Reduced use of costly pesticides
  • Development of pest-resistant crops
  • Improved nutritional quality of food
• Ethical considerations of Genetic Engineering

  • New proteins in GM foods may cause allergies
  • Companies engineering crops to be sterile, harming farmers
  • Welfare of animals
  • Potential use in chemical/biological warfare
  • Genes accidentally incorporated into harmful bacteria
  • Genetic engineering may not be accessible to all