DNA replication

• What is the purpose of DNA replication?

  To ensure daughter cells receive full DNA
• What does semi-conservative replication mean?

  Half the strands are from the original DNA
• What enzyme breaks hydrogen bonds during DNA replication?

  DNA helicase
• What role do free nucleotides play in DNA replication?

  They pair with complementary bases on templates
• What type of bonds are formed between nucleotides during DNA replication?

  Phosphodiester bonds
• What are the two ends of a DNA strand called?

  3' and 5'
• In which direction does DNA polymerase add nucleotides?

  To the 3' end of the growing strand
• What are the steps of DNA replication?

  1. DNA helicase breaks hydrogen bonds.
  2. Strands unwind into single polynucleotide strands.
  3. Each strand serves as a template.
  4. Complementary base pairings occur.
  5. DNA polymerase joins nucleotides.
  6. Phosphodiester bonds form between strands.
• How do the strands in the double helix relate to each other?

  They are antiparallel
• What evidence supports semi-conservative replication?

  • Meselson and Stahl's nitrogen isotope experiment
  • Bacteria grown in light and heavy nitrogen
  • Centrifuge results showed hybrid DNA
• What happens to DNA in a centrifuge during the experiment?

  Heavy DNA settles at the bottom
• What would indicate conservative replication in the centrifuge results?

  Light DNA at the top, heavy at the bottom
• What is the replication fork in DNA replication?

  • The area where DNA helicase unwinds the double helix
  • Shaped like a Y
  • Site of active DNA synthesis
• What are Okazaki fragments?

  Short DNA segments on the lagging strand
• What enzyme joins Okazaki fragments?

  DNA ligase
• What was Griffith's experiment about?

  • Showed transformation in bacteria
  • Pathogenic and non-pathogenic strains used
  • Demonstrated genetic material transfer
• What is transformation in bacteria?

  Change in genotype due to foreign DNA
• What evidence supports DNA as hereditary material?

  • Experiments with radioactive proteins and DNA
  • Only radioactive DNA showed transfer
  • DNA provides instructions for viral replication
• What did the radioactive DNA experiment show?

  DNA can pass and produce genetic information