The DNA inside the cells

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READ: Background DNA replication is the process whereby the cell makes an identical copy of the whole genome (all the DNA inside the cell) in preparation for cell division. It involves a number of steps that are catalyzed and coordinated by a number of different proteins. To prepare for this lab, you are going to work through a computer simulation of the process and answer some questions about it. Then you will model the process of DNA replication using paper DNA and proteins.

HW Assignment
❖ Go to the following website: http://www.phschool.com/science/biology_place/biocoach/dnarep/intro.html

● A google search for “DNA Replication phschool” might be easier than typing in the URL. It should be the first hit.
● CLICK on Concept 4: Biosynthesis of DNA (in the panel on the left side of the screen). Then click on the purple “Review” button.

  1. In which direction does the DNA polymerase move?
  2. What is the substrate for DNA polymerase?
  3. How does DNA polymerase know which base to add to the growing chain?
  4. What type of bond is formed between the growing DNA chain and the new nucleotide?

● Click on “Concept 5: Replicating Antiparallel DNA Strands” then on the “Review” button in the upper right corner of the screen. Watch the 5 steps of DNA replication and answer the following questions:

  1. In an unlabeled diagram, how can you identify the leading strand? ௿௼
  2. In an unlabeled diagram, how you can identify the lagging strand?
  3. Why are there Okazaki fragments in the lagging strand but not the leading strand?
  4. What nucleic acid polymer is created first on the lagging strands? Should there also be this polymer in the leading strand?
  5. Why is it necessary to have an RNA primer before DNA is produced?
  6. What does DNA Polymerase I do? Why is this important?
  7. What does DNA ligase do? What would happen if there wasn’t DNA ligase around during DNA replication?
  8. Why does the animation call DNA replication “semi-continuous”?

PART B:
● Test your understanding: One you have completed the modeling activity, do this matching exercise to check your understanding of the fundamentals of this process. Write the right term next to its definition:
● Word Bank(13 words each for each definition):
Helicase Primase 3’ end Origin of Replication DNA Polymerase Lagging strand 5’ end Semi-conservative Replication Ligase Leading Strand Replication Bubble Conservative Replication RNA primer Okazaki fragments Replication Fork Dispersive Replication

  1. Enzyme that builds DNA strands but can only add onto existing strands
  2. Enzyme that connects two fragments to close the gap between them
  3. Type of replication that takes place
  4. The space that is opened up by one helicase
  5. The circular space opened up by two helicases moving in opposite directions
  6. Enzyme that opens up or unzips the DNA double stranded helix
  7. Enzyme that creates a complementary RNA fragment next to DNA about to be replicated
  8. The strand created by a DNA Polymerase following the helicase
  9. The strand created by several DNA Polymerases moving in the opposite direction from the helicase.
  10. The fragments of the lagging strand
  11. A location in the DNA that the helicase starts to unzip and open up the DNA helix.
  12. Small segments of RNA that DNA polymerase adds DNA nucleotides to
  13. The end of an existing strand that nucleotides can be added to

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