DNA Replication

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DNA Replication
2015-04-20 11:22:11
dna replication biology velasco bio120
an indepth overview of DNA replication
Show Answers:

  1. Describe the semi conservative model of DNA
    porposed by Watson and Crick, where the one parental strand is kept intact and used as a template during DNA replication. As a result, each daughter strand during the first replication would have one intact parental strand and one newly synthesized strand.
  2. What experiment supported the semi conservative model?
    • Meselson and Stahl
    • Labeled e.Coli with heavy nitrogen 15 then transferred the medium to with nitrogen 14. When they centrifuged, they found that the first replication had a dark/light mixture band with and a light band.
  3. Describe the Griffith experiment, what they used and the conclusion
    • They injected four sets of bacterial strains into mice. S-heated cells, S- live pathogenic cells, R-non pathogenic, and a mixture of S-heated and R
    • Although the S-heated cells did not kill the mice, the mixture of S-heated and R killed the mice.
    • Identified that some substance caused a heritable change in the R cell.
  4. Describe the Hershey and Chase experiment, what did they do and what was the conclusion
    • Identified whether proteins or DNA was involved with virus replication (by the infection of host cells) and which molecule would enter the cell. 
    • Used bacteriophages and color coded proteins with sulfur and DNA with phosphorous.
    • After centrifuging the phages, identified DNA as the genetic material.
  5. Describe prokaryotic DNA replication and how it is different from eukaryotic replication
    For prokaryotes, they have only one origin of replication and is synthesized in both directions, ending at the DNA replication terminus.

    For eukaryotes, there are multiple origin of replications and replicates in only one direction from the 3' to 5' on the template strand.
  6. Describe DNA helicase and its role
    Helicase unzips the parental strand at the origin of replication by breaking the hydrogen bonds between the nitrogenous bases
  7. what is the origin of replication and how many can the eukaryotic cell have?
    The origin of replication is the area where DNA is replicated. For eukaryotes, it is consists of two replication forks.
  8. What type of bonds are broken by DNA helicase
    hydrogen bonds
  9. What is SSBP (single strand binding protein) and its role during DNA replication
    a protein that binds to the DNA at the replication fork and stabilizes the DNA from rejoining, keeping the two stands apart.
  10. What is topoisomerase and its role?
    A protein that stabilizes the double helix region right next to the replication fork. It aids in relieving the torsional strain when DNA unwinds
  11. Describe DNA primase and it's role
    DNA primase is an enzyme that creates RNA primers,
  12. What does DNA primase require to create RNA primer?
    • template strand
    • 3'-OH
  13. How many DNA primase is needing for the leading and lagging strand?
    • leading strand: 1
    • lagging strand: several
  14. what is DNA polymerase and its role for DNA replication?
    creates the complementary daughter strand by adding complementary nucleotides
  15. what molecule initiates the DNA polymerase?
    RNA primer
  16. At what end does DNA polymerase adds nucleotides?
    3'-OH of RNA primer
  17. What is the difference between DNA polymerase III and DNA polymerase I?
    • DNA polymerase III: adds nucleotides from 3' end of RNA primer
    • DNA polymerase I: replaces RNA primer and adds nucelotides. a holoenzyme, it is involved in proofreading as well.
  18. Which polymerase replaces the RNA primer for prokaryotic cells
    DNA pol I
  19. Describe the role of DNA ligase
    links okazaki fragments together
  20. What are telomeres and what is their function?
    telomeres: guanine rich sequences on the template strand that encode for telomerase attach at the end of the lagging strand
  21. What are some problems that occur toward the end of DNA replication?
    towards the end of DNA replication, the lagging strand runs out of enough nucleotides for the RNA primer to base pair therefore, the addition of DNA nucleotides is aided by telomeres and telemerases.
  22. What are telomerases?
    enzymes that bind to the telomere sequences on the DNA strand and synthesizes new nucleotide sequences.
  23. what is DNA ligase and describe it's role
    links the okazaki fragments together to form a continuous strand, by replacing the RNA primer
  24. What are the building blocks of nucleic acids
    nucleoside triphosphates
  25. What are nucleoside triphosphates, their function and give some examples
    nucleoside triphosphates are energy rich molecules that phosphorylate and form nucleic acids.ex) ATP
  26. What are dNTPS
    nucleosides triphosphates with a deoxyribose
  27. How does DNA repair itself?
    undergoes a process called mismatch repair.
  28. What is nucleotide excision
    the process of removing a sequence of nucleotide errors when repairing DNA