6-2 quiz questions

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You are fortunate to be in a strong academic environment with active research projects ongoing with faculty support! Dr. Posner and his research students are interested in how proteins in the lens help to keep the lens transparent as it ages, and what role they play in building the lens in the first place. Why do this type of research in a fish? It turns out that fish lenses have most of the same proteins as ours, and it is much easier to get your hands on fish lenses for research than human lenses. They also use zebrafish, and several other species of fishes, to understand how lens proteins have evolved to function at different temperatures. You can read more about their research here or see one of their latest research papers here. The video at the bottom shows our zebrafish room here at Ashland University.

The zebrafish is also used to study many other aspects of vision. One of its most interesting uses is to identify novel genetic mutations that affect vision. In this approach, researchers intentionally use chemicals to cause mutations in the zebrafish genome and then look for new individuals that do not see properly. If you find some of those you can try to determine what gene was affected and maybe identify genes that are not yet known to be involved in vision or blindness. That would allow you to investigate the role played by the protein encoded by that gene. But how do you give a fish a vision test?

Directions

For this assignment you will learn about a test that works on both humans and fish called the optokinetic response (OKR). I would then like you to read portions of a scientific paper that used this technique to identify fish with faulty vision to idenfity the genes involved. You should:

With this background on OKR response in zebrafish in mind I would like to use a scientific paper from the journal PLoS Genetics to answer the questions below. This is an example of “primary literature”, a research paper written by scientists that presents new data that have never been published before. This paper not only disseminates new research to the scientific community, but gives other researchers the opportunity to try these experiments themselves to see if the paper is accurate. Remember that science is a self-correcting enterprise. Scientific ideas are valid until someone shows that you are wrong. If others can’t disprove your work, or confirm it with their own studies, your hypotheses become even stronger. Scientific hypotheses that withstand a great deal of scrutiny and still hold up become “theories.”

Use this paper to answer the questions below. You do not need to read the entire paper, but do scroll through to see what is involved. For example, check out the Material and Methods section, which details exactly how the research was done so that others can duplicate it if they wish. You will only need to look through the synopsis, introduction and discussion to answer the questions below. Please submit the following questions for your Quiz points for this module (20 points)

  • According to the “Introduction” and “Synopsis” of this paper, what was the goal of the authors? What was the purpose of this study?
  • The authors used a chemical to mutagenize (cause DNA mutations in) their zebrafish. How did the authors determine if the offspring of these zebrafish inherited mutations that affect vision?
  • Check out this video from the paper comparing a normal baby fish (on the left) and mutant fish (on the right) in an OKR device. The striped drum is not turning as the clock counts down from -60 to 0 seconds. Any movements during this time are random. When the clock reaches 0 sec they turn on the rotating stripes. Watch the difference in how the two fish respond from 0 to 60 seconds.
  • According to the “Discussion” section, how many new genetic mutations did they find that affect vision? In what parts of the visual system do they think these genes are used?