DNA BUILDING

1. Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complimentary base pairing.

Our DNA consists of two halves, antiparallel strands of each other, both with sugar-phosphate backbones. They both contain all four nucleotides, but the opposite of each other for complimentary base pairing. A to T, and G to C. The whole DNA itself is in the shape of a double helix.

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.

This model helps us visualize how the nucleotides interact with each other, and the overall shape of DNA to an extent. As for what can be done to improve the model, we could have something unique to represent the hydrogen bonds between the bases, as guanine and cytosine have three hydrogen bonds, while adenine and thymine only have two (possibly another bead to represent a hydrogen bond each, two beads between adenine/thymine, and three beads between guanine/cytosine). If we were to go for high detail, we could also have separate beads for the phosphate and sugar in the backbone.

 

Models of DNA:

Single Strand

 

Untwisted DNA

 

Twisted DNA

 

DNA REPLICATION

1. When does DNA replication occur?

DNA replication occurs before cell division takes place. It duplicates the DNA to share it with the newly made cells.

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

First, the DNA strand unzips with the helicase, then new strands form in each unzipped side, through complimentary base pairing and the polymerase. Finally, the two strands separate fully, completing the replication process. The process occurs differently on the leading and lagging strand due to the direction the ligase reads the individual strands, one side will always be slower than the other since it is forced to read the DNA backwards.

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

To demonstrate complimentary base pairing, we linked the white pipecleaners from both sides together, shaping them like hooks. As for the joining of adjacent nucleotides, we has the ligase present beside the polymerase. Our model was well suited for this activity in some ways since it was a very simplistic model, making it easier to understand. It was a bit inaccurate though since we had limited materials and the size of our model limited how much we could fit and display for it.

 

Models of DNA:

DNA Starting to Unzip

 

DNA Separating Strands

 

DNA Replicating