Science Buddies: "Ask an Expert"

Hi,
I decided to change my science fair topic again. Now I'm interested in the effects of UV rays on yeast colony growth by exposing different petri dishes (with yeast colonies on them) to different durations of time under the UV ray light source. However, that seems a tad simple, and I was wondering how I could make it more complicated...and up to a high school level. I was thinking that a comet assay might be a cool idea and involve the DNA damage of the yeast cells, but the chemicals may be too dangerous and the science fair committee may not approve it. I was also looking into maybe different extremities of UV light rays...and my science teacher brought up an interesting topic. She said that some strains of yeast need specific nutrients (?) and that maybe under the UV light rays the DNA may change so much that it won't need that nutrient anymore (?). However, I can't find these strains of yeast while I was doing research online.

On a separate thought, what if I tested how adding vitamins would affect yeast cell growth? And then also test it under a UV light ray source? How does that sound?

One last thing...my science teacher said that she doesn't see the overall PURPOSE of this science fair project...why would it be necessary to know this information?

Thank you so much!

Hi there,

You have a very interesting idea!

I think that looking at two factors simultaneously (UV light levels and vitamins) would help make your project more complicated and thus at a high school level. You will need to be very careful in your experimental design to make sure that you can understand each effect (UV and vitamins) independently of each other.

One thought I had regarding relevance is the increase in UV rays penetrating our atmosphere. This would explain how that environmental change would affect yeast. Some people may not care very much about yeast, but it gives an example of an organism that *may* benefit from an increase in UV light penetration (or may not - I don't know!).

Hope that helps!

Heather

Hi,
If I decided to do a project something like "The DNA Damage of Ultraviolet Rays on Yeast Colony Growth", I would probably use a comet assay to measure the DNA damage (http://docs.google.com/viewer?a=v&pid=g ... Rbyw&pli=1). The purpose would relate to what Heather said, and how increasing UV rays are affecting organisms...I could also relate it to how the sun is causing harm at the beach over a duration of time (?).

Another thing I could do:
Relating UV intensity to vitamins, and which vitamins allow the yeast to be least affected by the UV rays (at different intensities). If I did this my science teacher said I would need to use "defined media" instead of the nutrient plate. I'm not quite sure what this is?

My science teacher mentioned a "liquid culture"...except I'm not quite sure what it is, even when I searched it on google. Is there one of the two projects which should be avoided for a reason, or either would work?

Thanks!
Margaret Chuang

Here is a website that discuss different projects about yeast and UV. http://www-personal.ksu.edu/~bethmont/rl2k/lab2.html You can obviously grow fungus on a agar plate, but using liquid medium with nutrient can also be used. Here is a picture of the liquid medium. http://www.tradekorea.com/product-detai ... Media.html# Once you decide on what yeast to use than you can select the media base on the type of yeast that you selected.

Michael