DNA Structure (OCR Gateway GCSE Biology: Combined Science)

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DNA is a Polymer

  • DNA, or deoxyribonucleic acid, is the chemical molecule that contains the instructions for growth and development of all organisms
    • DNA is the genetic material that determines the characteristics of all living organisms
    • DNA carries a set of chemical instructions to make all the proteins required for life
    • Except for identical twins every person's DNA is unique
  • DNA is contained in structures called chromosomes
  • In eukaryotic cells, chromosomes are located in the nucleus
    • DNA is classed as a polymer (a molecule made from many repeating subunits called monomers)
      • Monomers are the small basic units that can make larger complex molecules
      • In DNA the individual monomers are called nucleotides
      • The nucleotides are joined together to form a single long chain/strand

DNA, chromosomes and the nucleus, IGCSE & GCSE Biology revision notesDNA, chromosomes and the nucleus

DNA Forms a Double Helix

  • DNA takes the form of a double helix
  • Two long polymer chains/strands of nucleotides coil around to make a double helix
    • The double helix is a double-stranded spiral
    • It is similar to a twisted ladder

DNA double helix formation, downloadable AS & A Level Biology revision notes

The structure of DNA showing the double helix

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Author: Phil

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.