replication of DNA 2

• DNA replication occurs prior to cell division
• DNA polymerase

  The enzyme that replicates DNA
• DNA polymerase requires a primer to start DNA replication
• DNA replication


  1. DNA is unwound and hydrogen bonds between bases are broken – forming two template strands

  2. Primer attaches to a short sequence on the DNA allowing the DNA polymerase to bind

  3. DNA polymerase will add nucleotides using the complementary base pairing rule to the deoxyribose (3') end of the NEW strand which is forming
• Primer


  A short strand of nucleotides which binds to the 3' end of the template, allowing DNA polymerase to add new nucleotides
• DNA replication requires the use of ATP, free DNA nucleotides and other enzymes throughout the process
• DNA polymerase


  Works in a 5' to 3' direction, can only add nucleotides to the 3' end of the growing strand
• One strand is replicated continuously, called the leading strand
• The opposite strand has to be replicated in fragments, called the lagging strand, requiring many primers and the enzyme ligase to join the fragments
• Polymerase chain reaction (PCR)

  1. DNA is heated to break hydrogen bonds and separate strands

  2. DNA is cooled to allow primers to bind to target sequences

  3. DNA polymerase (Taq) replicates the region of DNA
• PCR amplifies DNA using complementary primers for specific target sequences
• Practical applications of PCR

  • Amplify DNA to help solve crimes
  • Settle paternity suits
  • Diagnose genetic disorders