L8: DNA Replication

• Who delivered Lecture 8 in 2024 on DNA replication?

  1. Robert Spooner
• What significant genetic concepts were introduced by Morgan and Mendel?

  Sex linkage and the principles of inheritance
• What is the length of the E. coli genome?

  4639 kb
• How is the total length of the E. coli DNA calculated?

  By multiplying the number of base pairs by the spacing between base pairs
• What is the total length of E. coli DNA in meters?

  1.6 mm
• What is the haploid genome size of humans?

  3.2 Gbp
• How much DNA does a typical somatic cell in humans contain?

  6.4 Gbp
• What is the total length of DNA in a typical human somatic cell?

  Approximately 2.2 m
• How does the amount of DNA in a human body compare to the distance to the sun?

  Each person has enough DNA to stretch to the sun and back approximately 730 times
• What is the diameter of a DNA duplex?

  2 nm
• What is the structure of chromatin fiber?

  30 nm diameter
• What must happen to DNA during cell division?

  DNA must be decompacted and copied faithfully
• What is the error rate during DNA replication?

  Approximately 1 in 10^9 base pairs
• What did the Watson-Crick model predict about DNA replication?

  It suggested a possible copying mechanism for the genetic material
• What does semi-conservative replication mean in DNA replication?

  Each daughter DNA molecule contains one parental strand and one newly-replicated strand
• What are the two predictions of the Watson-Crick model regarding DNA strands?

  Strands are held together by base-pairing and are complementary
• What are the three models of DNA replication proposed before the Meselson and Stahl experiment?

  Semi-conservative, conservative, and dispersive models
• What technique did Meselson and Stahl use to test DNA replication models?

  CsCl equilibrium density gradient centrifugation
• How does CsCl equilibrium density gradient centrifugation work?

  It separates molecules based on their densities
• What type of nitrogen was used in the Meselson and Stahl experiment?

  14N and 15N
• What is the density of 14N-labelled DNA compared to 15N-labelled DNA?

  14N-labelled DNA is lighter than 15N-labelled DNA
• What was the outcome of the Meselson and Stahl experiment regarding DNA replication?

  It confirmed that DNA replication is semi-conservative
• Who discovered DNA polymerase?

  Arthur Kornberg
• What is required for DNA polymerase to replicate DNA?

  A template DNA, deoxynucleotide triphosphates, Mg$^{2+}$, ATP, and a primer
• What happens to dNTPs after the DNA replication reaction?

  dNTPs remain soluble while polynucleotides precipitate
• What additional functions does DNA polymerase I (Pol I) have?

  It has editing and proofreading functions
• Which DNA polymerase is essential for DNA replication in E. coli?

  DNA polymerase III (Pol III)
• What is the significance of the Central Dogma in molecular biology?

  It describes the flow of genetic information from DNA to RNA to protein.
• How is bacterial DNA compacted?

  By looping and supercoiling.
• What role do nucleosomes play in DNA organization?

  Nucleosomes help package DNA into a compact structure.
• What is the implication of the semi-conservative model of DNA replication?

  It ensures genetic continuity by preserving one parental strand in each daughter molecule.
• What are the specific conditions required for DNA polymerase activity?

  A template DNA, deoxynucleotide triphosphates, Mg$^{2+}$, ATP, and a primer are required.
• What was the significance of the Meselson and Stahl experiment?

  It confirmed the semi-conservative model of DNA replication.
• What are the differences between DNA polymerases I and III?

  Pol I has proofreading functions, while Pol III is essential for DNA replication.
• What enzyme is capable of replicating DNA?

  A DNA polymerase
• What conditions were required for Kornberg's extract to make new DNA?

  A template DNA, deoxynucleotide triphosphates, Mg$^{2+}$, ATP, and a primer with a free 3' OH
• What happens to dNTPs and polynucleotides after the reaction mixture is treated with acid?

  dNTPs remain soluble, but polynucleotides precipitate
• What was found in the pellet after treating the reaction mixture with acid?

  32P was found in the pellet
• In which direction are new strands extended by a polymerase?

  New strands are extended in the 5' → 3' direction
• What additional activities does Pol I have?

  Pol I has editing/proof-reading functions and can correct mistakes