B1.2 - DNA

• Deoxyribose Nucleic Acid (DNA)


  Contains all of an organism's genetic material (the chemical instructions it needs to grow + develop)
• DNA


  • Arranged into chromosomes (long molecules of coiled up DNA) which is divided up into short sections called genes
• Polymer


  Large complex molecules made from long chains of monomers
• Monomer


  Small, basic molecular units
• DNA


  • In the shape of a double helix which is a double stranded spiral
  • Each strand is made up of a chain of nucleotides
  • Each nucleotide contains a small molecule called a "base"
• DNA bases


  • Adenine
  • Thymine
  • Guanine
  • Cytosine
• Complementary base pairing


  The curly letters go together, each base forms cross links to a base on the other strand, bonding with hydrogen bonds
• DNA nucleotide


  • Has the same sugar and a phosphate group, the base is the only part that varies and is attached to the sugar
• Gene


  Sections of DNA found on chromosomes, contains instructions for making proteins
• Protein


  Made of amino acids, order of amino acids determines the protein, order of bases determines the amino acids
• Levels of organisation


  • Nucleotide
  • Gene
  • Chromosome
  • Nucleus
  • Cell
• Transcription


  1. Unzipping of the DNA molecule around the gene allowing the single RNA bases to attach creating a strand of mRNA (messenger RNA) in the nucleus

  2. mRNA strand leaves the nucleus to enter the cytoplasm through the nuclear pore
• Translation


  1. mRNA attaches to the ribosome which moves along the mRNA strand decoding it into base triplets (a codon)

  2. Each codon codes for a particular amino acid

  3. A polypeptide (chain of amino acids) is created by tRNA (transfer RNA) codons
• Differences between DNA and RNA

  • Thymine is replaced by Uracil
  • RNA is a single strand