DNA Model

1. Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complementary base pairing.
2. How does this activity help model the structure of DNA? What changes could we make to improve the accuracy of this model? Be detailed and constructive.

–           DNA is made of nucleotides and the nucleotides have sugars(deoxyribose), phosphate groups, and nitrogen bases. It is the shape of double helix. The 2 strands in DNA are described as antiparallel and complementary base pairing. Antiparallel literally means the strands are read in “opposite” direction. Also, complementary base pairing is the process that the base always pairs with specific partner; Adenine always pairs with Thymine and Cytosine always pairs with Guanine. This activity was helpful to me to understand the structure of DNA by allowing my group to create a code using DNA language ourselves. We used blue and white pipe cleaners, and coloured beads to represent phosphate groups, hydrogen bonds, sugars, and nitrogen bases. If we reduce the length of the white pipe cleaner, it would be looked more accurate because in reality, nothing is separated between the nitrogen bases and the backbone. Actually, my fingers hurt because of the wires, but it helped me to understand and demonstrate the DNA structure.

DNA Replication Model

1. When does DNA replication occur?
2. Name and describe the 3 steps involved in DNA replication. Why does the process occur differently on the “leading” and “lagging” strands.
3. The model today wasn’t a great fit for the process we were exploring. What did you do to model the complimentary base pairingand joining of adjacent nucleotidessteps of DNA replication. In what ways was this activity well suited to showing this process? In what ways was it inaccurate?

• DNA replication occurs period of cell division and there are 3 stages involved in DNA replication. The 3 stages are Unwinding, Complementary base pairing, and Joining. Firstly, in “Unwinding” step, the two strands that make up DNA unwind and unzip. The DNA double helix unwinds and the two strands of DNA separate. Next step is “Complementary base pairing” and in this step, new nucleotides move in to pair up and with bases of each strand of DNA. Lastly, in “Joining” part, the adjacent nucleotides join to form new strands. This step is carried out by an enzyme called DNA polymerase. A leading strand is synthesized in the 5’ to 3’ direction while a lagging strand is synthesized in the 3’ to 5’ direction. The leading strand is synthesized continuously, but the lagging strand is synthesized in fragments. Also, DNA ligase glues fragments. I had to attach white pipe cleaners which represent the nucleotides. For the leading strand, it should be attached from the top down while the lagging strand should be attached from the bottom up. Also, it was inaccurate because the model could not exactly replicate the bonds between the backbone and the nitrogen bases. However, visually, it was almost same with real DNA, so this activity well suited. Because it showed the same sequence DNA which was split to form same sequence of daughter DNA.