1. When does DNA replication occur?

DNA replication will occur just prior to cell division. DNA will undergo its semi-conservative process and will begin its three stages of replication.

2. Name and describe the 3 steps involved in DNA replication. Why does the process occur differently in the “leading” and “lagging” strands?

The three steps involved in DNA replication are as follows; DNA unzipping and unwinding, complementary base pairing, and joining of adjacent nucleotides. During the first stage of replication the “parent” DNA molecule untwists itself from its double helix shape to a rather flat straight molecule resembling a ladder. During the second stage the bases originating from the now “unzipped” parent molecule will pair with their complementary bases (A with T, C with G). During the final stage the now paired base nucleotides will bond together through hydrogen bonding and this is accomplished with help from DNA ligase. DNA ligase is however only able to “read” the molecule and attach the new bases and backbone from 3’ to 5’ this results in one strand becoming the leading strand and the other becoming the lagging strand.

3. The model today wasn’t a great fit for the process we were exploring. What did you do to model the complementary base pairing and joining of adjacent nucleotides steps of DNA replication. In what ways was this activity well suited to show this process? In what ways was it inaccurate?

To demonstrate the process of complementary base pairing and the joining of adjacent nucleotides, our group detached several but not all of the joint bases and placed the Fuzzy Peach in the center along the “unzipping” DNA to represent DNA Helicase. We then decided to use a blank sheet of paper with drawn-on arrows to indicate other components such as the directions of the “leading and “lagging” strands. I think this activity is generally quite well suited for the demonstration of the process however does not explicitly allow clear representation of the directions in which the enzymes will read etc.