DNA

• The genetic material in the nucleus of a cell is composed of a chemical called DNA
• DNA is a polymer made up of two strands forming a double helix
• DNA is contained in structures called chromosomes
• A gene is a small section of DNA on a chromosome
• Each gene codes for a particular sequence of amino acids, to make a specific protein
• The genome of an organism is the entire genetic material of that organism
• The whole human genome has now been studied and this will have great importance for medicine in the future
• The genome is used to

  • Search for genes linked to different types of disease
  • Understand and treat inherited disorders
  • Trace human migration patterns from the past
• DNA is a polymer made from four different nucleotides
• Nucleotides consists of a common sugar and phosphate group with one of four different bases attached to the sugar

  A) Base

  B) Phosphate

  C) Sugar

  
• DNA contains four bases, A, C, G and T
• A sequence of three bases is the code for a particular amino acid
• The order of bases controls the order in which amino acids are assembled to produce a particular protein
• In the complementary strands of DNA a C is always linked to a G on the opposite strand and a T to an A
• Mutations occur continuously but most do not alter the protein, or only alter it slightly so that its appearance or function is not changed
• A few mutations code for an altered protein with a different shape so an enzyme may no longer fit the substrate binding site or a structural protein may lose its strength
• Not all parts of DNA code for proteins
• Non-coding parts of DNA can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed