1. Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complimentary base pairing.
DNA is a large polymer, made of nucleotide monomersand composed of 2 backbones of sugar-phosphate, shaped into a double helix (see picture below). The nucleotide bases are faced “into” each other and are formed by hydrogen bonding between their respective base pairs. Each base always bonds with the same partners which is known as complimentary base pairingwhere adenine bonds with thymine and guanine with cytosine. The two strands of sugar-phosphate are antiparallelstrands, meaning that they read in opposite directions.
2. How does the activity help model the structure of DNA? What changes could we make to improve the accuracy of this model? Be detailed and constructive.
This assignment does adequate job of representing the final produce and structure of the DNA as well as the daughter and parent relationship. However, it is difficult to show the steps leading up to the DNA’s final form. For instance, when unwinding or unzipping the DNA, the activity couldn’t accurately show the enzymes activity working in detail.
3. When does DNA replication occur?
During the process of mitosis, DNA replication occurs in the synthesis phase in the daily life cycle of the cell.
4. Name and describe the 3 steps involved in DNA replication. Why does the process occur differently on the “leading” and “lagging” strands?
Unwinding. This is where the two strands of the helix unzip when the helicase runs down the middle of the DNA, breaking the hydrogen bonds between the base pairs, causing the enzyme to unwind.
Complimentary base pairing.The nucleotides move into place and form hydrogen bonds with a different partner on the strand which is facilitated by the DNA polymerase.
Joining. This is when the nucleotides on the new strand form covalent bonds.
The process of DNA replication occurs in different ways because in the leading strand, it forms continuously as the DNA unzips whereas in lagging strands, only fragments form as DNA unzips.
5. 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 going 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?
In the process of complimentary base pairing, my team placed each respective nucleotide by its pair while using the blue big foot candy, as seen below, to demonstrate the process of the DNA polymerase moving the nucleotide together and the red big foot candy to connect them on the leading and lagging strands with each suitable nucleotide. For this particular activity, it was quite accurate in showing the nucleotides coming together, but rather difficult in providing a good visual aid to how the DNA ligase joins the nucleotides together. It was particularly tough for the specificity required in the lagging and leading strands as well because we had to make certain that the blue big foot was pointing the correct way because of which way the DNA has to read.
6. How is mRNA different than DNA?
DNA is composed of deoxyribose sugar, has thymine as one of the two pyrimidines, is present in the nucleus, and is double-stranded.
mRNA is composed of ribose sugar, has uracil that replaces thymine as one the pyrimidines bases, diffuses into the cytoplasm after synthesis, and is single stranded.
7. Describe the process of transcription.
Unwinding and unzipping of DNA.Firstly, a particular section of the complimentary base pairings unwinds, revealing one gene only, occurring when there is a protein deficiency.
Complimentary base pairing with DNA. Along one of the DNA strands, complimentary base pairing occurs with that strand and the incoming RNA strand through hydrogen bonding. (Uracil will bond with DNA’s adenine.)
Separation from DNA. Adjecent nucleotides form covalent bonds and builds RNA backbone. àRNA Polymerase (represented by the fuzzy peach)
RNA is released, moves out of the nucleus into the mitochondria and DNA reforms a double helix.
8. How did today’s activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?
This activity helped understand and demonstrate the basis of transcription and the steps that occur in this stage, though it was not as detailed as it could have been. My team and I found that there were some struggling points in terms of clarity in the model. For instance, in the first step, where one section of DNA was supposed to unwind, revealing just one gene, we ended up having no choice but to unwind the entirety of our DNA helix structure. Though we assumed that the DNA molecule we made was one gene, we had no real way of telling whether it was one gene or more. In addition, RNA must be refined in the nucleus before being released which was not demonstrated as best as it could have been. All that being said, this activity had a great overall imagine of the basic structure of DNA and RNA but, definitely lacked clarity specifically in terms of why DNA is structured this why, as well as how transcription and translation operates.