- Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complementary base pairings. DNA belongs to the group of molecules called nucleotides, which all contain a sugar, nitrogenous base and a phosphate group.
- 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. We used blue pipe cleaners with black beads to model the sugar and phosphate groups that make up the DNA backbone, as well as white pipe cleaners with coloured beads to represent the four nitrogenous bases. Each white pipe cleaner was hooked to the one across from it that held its complementary base pair; the hooks representing the hydrogen bonds. Reducing the length of the white pipe cleaner could make the model more accurate, as in reality there is nothing separating the nitrogenous bases from the backbone of the molecule.
- When does DNA replication occur? DNA replication occurs during mitosis. To create a clone of the cell it is dividing from, the nucleus must also contain an exact replica of the chromosomes and DNA in the previous cell and every other cell in the body for it to do its job properly.
- Name and describe the 3 steps involved in DNA replication. Why does this process occur differently on the ‘leading’ and ‘lagging’ strands? 1. Unwinding and ‘unzipping,’ this process is completed by the helicase, which runs down the strand of conjoined DNA and breaks the hydrogen bonds between the complementary base pairs, effectively creating two parent strands. 2. Complementary base pairing. Completed by the polymerase, it follows the helicase down the strand to pair the bases exposed on the parent strand. Because the strands are anti-parallel, the polymerases must travel in opposite directions. While one may be able to follow the helicase, the other must read chunks at a time in the opposite direction and backtrack to return to the helicase. 3. Joining of adjacent nucleotides. The ligase then follows the polymerase down the strand and joins the fragments together to create a fully formed backbone and newly replicated DNA molecule.
- The model today wasn’t a great fit for the process we were exploring. What did you do to model the complementary base pairing 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? The model was able to show the general placement of each part of the process but was not able to fully replicate the bonds between the nitrogenous bases and the backbone of the molecule.
- How is mRNA different from DNA? Besides having their own unique nitrogenous base, (uracil and thymine) DNA and mRNA are structurally different as well. While DNA can be up to 85 million base pairs long, mRNA is usually only 1000. Also, while DNA has two backbones made from the sugar deoxyribose, mRNA only has one, made from ribose.
- Describe the process of transcription. DNA unwinds itself from the chromosome it was contained in and is unzipped. An RNA polymerase reads the ‘sense’ strand and pairs the bases with their complementary RNA counterparts. Once complete, the newly formed mRNA molecule breaks off of the DNA, which re-zips itself and rewinds itself back into the chromosome it came from.
- How did today’s activity do a good job modelling the process of transcription? In what ways was our model inaccurate. The model did a good job showing the general structure of the molecules involved in the process but again did not properly show the proportions to which everything is actually to scale.
(Picture were not able to be uploaded at this time)