Recap

• DNA Structure:

  DNA is made of two strands of deoxyribose-phosphate backbone running antiparallel to each other from a 5' to 3' direction
• DNA Structure:

  4 bases of Adenine, Thymine, Cytosine and Guanine pair up complementarily to form a three-ring bridging structure held together with two or three hydrogen bonds
• DNA Organisation:

  DNA encodes information in the sequence of its bases

  • These bases sit inside two sugar/phosphate backbones that twist around each other into a double helix
• DNA Organisation:

  Histones are proteins that DNA winds around and they give the packaging of this molecule structure
• DNA Organisation:

  When DNA is not replicating or being transcribed and about to go into mitosis/meiosis, the chromosomes condense and you are able to see them separately under a microscope
• Chromosome Organisation:

  • A chromosome consists of two strands called (sister) chromatids, they are joined in the middle by a centromere
• Chromosome Organisation:

  • Chromosomes are only visible during cell division because they are formed during interphase when the DNA is replicated
• Chromosome Organisation:

  • Each sister chromatid on a chromosome contains identical genetic information so that each daughter cell also contains identical information