DNA Structure (OCR Gateway GCSE Biology: Combined Science)

• 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

• 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

The structure of DNA showing the double helix