Critical Thinking Questions
21. Explain Griffith’s transformation experiments. What did he conclude from them?
22. Why were radioactive sulfur and phosphorous used to label bacteriophage in Hershey and Chase’s experiments?
23. When Chargaff was performing his experiments, the tetranucleotide hypothesis, which stated that DNA was composed of GACT nucleotide repeats, was the most widely accepted view of DNA’s composition. How did Chargaff disprove this hypothesis?
24. Provide a brief summary of the Sanger sequencing method.
25. Describe the structure and complementary base pairing of DNA.
26. Prokaryotes have a single circular chromosome while eukaryotes have linear chromosomes. Describe one advantage and one disadvantage to the eukaryotic genome packaging compared to the prokaryotes.
27. How did the scientific community learn that DNA replication takes place in a semi-conservative fashion?
28. Imagine the Meselson and Stahl experiments had supported conservative replication instead of semi-conservative replication. What results would you predict to observe after two rounds of replication? Be specific regarding percent distributions of DNA incorporating 15N and 14N in the gradient.
29. DNA replication is bidirectional and discontinuous; explain your understanding of those concepts.
30. What are Okazaki fragments and how they are formed?
31. If the rate of replication in a particular prokaryote is 900 nucleotides per second, how long would it take 1.2 million base pair genomes to make two copies?
32. Explain the events taking place at the replication fork. If the gene for helicase is mutated, what part of replication will be affected?
33. What is the role of a primer in DNA replication? What would happen if you forgot to add a primer in a tube containing the reaction mix for a DNA sequencing reaction?
34. Quinolone antibiotics treat bacterial infections by blocking the activity of topoisomerase. Why does this treatment work? Explain what occurs at the molecular level.
35. How do the linear chromosomes in eukaryotes ensure that its ends are replicated completely?
36. What is the consequence of mutation of a mismatch repair enzyme? How will this affect the function of a gene?
37. An adult with a history of tanning has his genome sequenced. The beginning of a protein-coding region of his DNA reads ATGGGGATATGGCAT. If the protein-coding region of a healthy adult reads ATGGGGATATGAGCAT, identify the site and type of mutation.