Chapter 15 study questions
Are genes encoded by protein or DNA? Would you find proteins or DNA in chromosomes?
Describe the experiment of Hershey and Chase.
The reasoning behind the labeling in their experiment was that DNA contains phosphorus but not sulfur and proteins contain sulfur but not phosphorus.
Explain the reasoning behind the labeling in the Hershey and Chase experiment.
Illustrate the major features of DNA’s primary and secondary structure.
Explain the concept of DNA polarity.
DNA polymerase adds deoxyribonucleotides to the 3’ end of a growing DNA chain therefore DNA is always synthesized in the 5’ to 3’ direction.
Describe the DNA synthesis reaction catalyzed by DNA polymerase.
What does it mean to say that DNA is synthesized in the 5’ to 3’ direction?
Why is an RNA primer required during DNA synthesis?
What enzyme synthesizes the primer?
List the proteins required for DNA synthesis in E. coli , and describe the function of each. Imagine a collection of mutant cells, each with a mutation rendering one of these proteins non-functional. What would happen at the replication fork in each of these mutants?
The error rate during DNA replication averages less than one mistake per billion nucleotides (error rate < 1 x 10 -9 ). How is this extremely low error rate achieved?
What happens when a DNA polymerase inserts the wrong base into a sequence?
Mismatch repair occurs in the S phase.
When during the cell cycle does mismatch repair occur?
Why is it important for E. coli cells to distinguish the “old” strand from the “new” (i.e., newly synthesized) strand? How do they do so?
How can DNA be damaged?
Explain the mechanism by which damaged nucleotides are recognized and repaired.
How could defects in DNA repair pathways increase the risk of cancer?
DNA polymerase cannot copy the end of the lagging strand of a linear chromosome. Why not?
How do some cells avoid the problem of telomere shortening?