AP Biology Scientific Journal
Nimisha Jain
DNA THINKQUEST
1. Go to the following links:
http://www.pbs.org/wgbh/aso/tryit/dna/#
2. On the PBS site, read the DNA introduction, then proceed to the “DNA Workshop Activity.” Complete the activity.
3. Now watch the animation on the McGraw-Hill site.
4. In complete sentences, briefly summarize the process of DNA replication. Make sure you include the following terms: polymerase, primase, RNA primer, replication fork, 5’ – 3’, helicase, ligase, leading strand, lagging strand, complementary strand.
DNA replication begins when helicase unzips the DNA and breaks hydrogen bonds between the 2 strands. DNA polymerase can only add new nucleotides to a free 3’ strand of DNA. Synthesis of one strand of DNA (called the leading strand), continues in the 5’ to 3’ direction. In the lagging strand, which is the complementary strand, DNA polymerase can only add nucleotides to a free 3’OH. RNA primase attaches to DNA and synthesizes a short RNA primer. Then DNA polymerase adds nucleotides to the 3’ end of the RNA primer. Then RNA is replaced with DNA. Then DNA ligase forms a bond between 3’OH and the 5’ in front of it. Leading strand is synthesized continuously. Lagging strand is synthesized discontinuously.
5. Now, proceed to “All Wound Up” on the PBS site.
6. Briefly describe the structure of a chromosome in complete sentences. Include the major building blocks and how they are put together.
A single strand of DNA is what forms a chromosome. The DNA is wrapped around proteins that are called histones. The DNA wraps around the histone many times, so it is packed tightly.
7. Now looks at the “People” section on the PBS site.
8. Briefly outline the contributions of the following people in complete sentences: Wilkins, Watson, Crick, Franklin.
Franklin made advances in x-ray diffraction techniques with DNA. She also extracted finer DNA fibers than ever before and arranged them in a parallel manner. But Wilkins, her partner (they both had relationship issues as they both thought they were going to be the only one working on the DNA project but they were meant to work on it together), showed her research to Watson, since Wilkins was frustrated and his relationship with Franklin was already tense. So Watson and Crick worked together to create a visual model for DNA and show each strand of the DNA molecule was a template for the other from their own research and what they stole from Franklin.
9. Describe two controversies surrounding the race to discover the structure of DNA. What is your opinion about each? Would the same controversies exit today? Why or why not?
Well firstly, women scientists weren’t treated as well as male scientists. They had to sit separately, as Franklin couldn’t each lunch in the same room as the other male scientists. Such issues wouldn’t be a problem in U.S today, since they have laws against that. Secondly, if some scientist tried to steal some other scientist’s research, like Wilkins showing Watson Franklin’s research, they would be sued, since there are laws against that as well. For these reasons, I don't think problems such as these would be a huge concern in today's enviroment in the U.S.