- DNA replication occurs before mitosis because the cell realizes that it is becoming too big so it has to divide in order to keep doing its function. If the cell were to grow any bigger, it would not be able to do it’s job, so it divides into two daughter cells.
- The 3 steps involved in DNA replication are unwinding and unzipping, complementary base pairing, and the joining of opposite nucleotides. In the first step (unwinding and unzipping) a DNA helicase breaks the Hydrogen bonds which hold the nucleotides together. Once the bonds are broken by the helicase, the DNA structure unwinds. Then in complementary base pairing, DNA polymerase match the opposite nucleotides together; Adenine bonds with Thymine and Guanine bonds with Cytosine. Finally, in the final step, (joining of nucleotides) DNA ligase put these nucleotides together and creates two new strands of DNA. The 3 steps are different on the “leading” and “lagging” strands because the DNA polymerase can only read the DNA strand from 3′ to 5′ which means the lagging strand has to be read backwards. The “leading” strand is the one with the extra sugar at the beginning.
- By modelling these, we were able to represent how the hydrogen bonds break apart and the steps that follow. By using different candies, we were able to represent the polymerase, helicase, and ligase and there job pretty accurately. However, it was hard to tell which strand was the leading and lagging one based on the model. Also, since we used blue pipe cleaner for all the DNA strand backbones, you never got a clear picture of which one was the parent DNA strand vs the daughter strand.
