DNA structure

• Ribosomes


  Organelles that make proteins
• DNA


  Long strands made up of alternating sugar and phosphate sections
• Base


  One of four different compounds attached to each sugar in DNA
• Nucleotide


  Combination of a sugar, a phosphate, and a base
• DNA polymer


  Made up of repeating nucleotide units
• Group of three bases


  Codes for a particular amino acid
• Gene


  Made up of hundreds or thousands of bases
• Amino acid


  Assembled to produce a particular protein for use in body cells
• The order of the bases controls the order in which the amino acids are assembled
• Each gene codes for a particular combination of amino acids, which make a specific protein
• A change or mutation in a single group of bases can be enough to change or disrupt the whole protein structure and the way it works
• DNA molecule


  The way the bases join up is the key to the structure and functioning
• Complementary strands of DNA

  1. C is always linked to G on the opposite strand

  2. T is always linked to A
• This holds the structure of the DNA double helix together
• It is also key in the way the information from the genes on the DNA is translated into proteins in the cell
• Protein synthesis in the cell

  1. Controlled by the DNA in the nucleus in a sophisticated series of steps

  2. Genes in the DNA produce a template for the protein

  3. The template reflects the sequence of bases in the DNA, but it is small enough to leave the nucleus through the pores in the nuclear membrane

  4. The template leaves the nucleus and binds to the surface of a ribosome

  5. The cytoplasm contains carrier molecules, each attached to a specific amino acid

  6. The carrier molecules attach themselves to the template in the order given by the DNA

  7. The amino acids are joined together to form a specific protein

  8. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order until the template is completed

  9. The protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids

  10. Once the protein chain is complete the molecule folds up to form a unique shape that will enable it to carry out its functions in the cell
• Any change in the order of the bases in the DNA structure of a gene will alter the template that is made
• A different template may result in a different sequence of amino acids joining together and so result in a change in the protein synthesised by a gene