1.2

• DNA is made up of components called nucleotides.
• Nucleotides contain:

  Phosphate

  Deoxyribose Sugar

  Organic Base
• The backbone of the DNA is called the sugar-phosphate backbone.
• Complementary base pairing:

  Adenine with Thymine

  Guanine with Cytosine
• Bases pair together by weak hydrogen bonds
• DNA structure:

  Anti-parallel

  Double stranded

  Double helix
• The 5' end of the DNA strand is found next to the phosphate.
• The 3' end of the DNA strand is found next to the deoxyribose sugar.
• First step of DNA replication:

  DNA unwinds, breaking the hydrogen bonds between the bases.
• DNA Replication, leading strand:

  1. A primer attaches to the 3' end, by complementary base pairing.
  2. DNA Polymerase starts adding nucleotides, by complementary base pairing
• A primer is a short sequence of nucleotides.
• In the lagging strand, fragments of DNA are joined together by ligase.
• In the lagging strand, several primers attach to the 3' end.
• PCR amplifies DNA using complementary primers for specific target sequences.
• PCR Stage 1:

  DNA sample is heated to around 90 degrees to break hydrogen bonds between bases
• PCR Stage 2:

  DNA sample is cooled to around 65 degrees to allow primers to bind
• PCR Stage 3:

  DNA sample is heated up to around 75 as it is the optimum temperature for heat-tolerant DNA polymerase.
• PCR can be used to solve crimes and settle paternity suits.
• Gene expression involves the transcription and translation of DNA.