In some sense, this means that duplicating RNA would be easier, or at least take one fewer step. As I’ve already talked about, DNA polymerase can’t add a new nucleotide to form a DNA strand without having an RNA primer first. One of the major questions to ask is, why does our body store genetic information as DNA rather than RNA? It’s a fair question. Understanding DNA replication better in turn gave me a more nuanced appreciation of the grand theme of evolution of life. I also realized for the first time why Watson and Crick’s discovery of the double helix structure was truly so essential – it defines the antiparallel nature of complementary DNA strands, which in turn drastically influences the way replication must occur. Overall, I learned that something as simple as duplicating the DNA in our body is a frightfully complex activity, involving many more enzymes and steps than I had previously thought. In other words, a single DNA polymerase adds new nucleotides continuously on one strand but discontinuously on the opposite strand. Then a second DNA polymerase molecule traveling in the opposite direction seals the gaps. This had always been quite confusing for me, but through the process of making the video I realized what this meant for the first time – the presence of Okazaki fragments. While DNA polymerase traveling in one direction can certainly add nucleotides continuously on one strand (the leading strand), the antiparallel nature of complementary DNA strands prevents polymerase from adding nucleotides continuously on the opposite strand (the lagging strand). Second, this fact also accounts for the phenomenon of the lagging vs. First, it means that DNA polymerase must have some starting material before it begins creating a new, complementary DNA strand – so replication begins with the formation of an RNA primer. The second goal we had was to emphasize the fact that DNA polymerase can only add new nucleotides to the 3′ end of an existing nucleotide. I did not know that such binding proteins were so critical until this activity. ![]() One nuance about this process I learned was that DNA replication actually requires binding proteins to attach to the original DNA strands and keep them separated. With so many enzymes at work, this was definitely a challenge. We had to think before every step to ensure we got every detail right, from the direction in which helicase moves to create the replication fork down to the role of ligase to “glue” the sugar phosphate backbone of the newly added nucleotides together. We hope we drew specific attention to these with the balls of pipe cleaners labeled with white construction paper. First, we tried to accurately demonstrate the action of all the various enzymes involved in this process, from DNA polymerase to ligase. While making the video, we had a couple of specific goals in mind.
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