Researching a DNA extraction project

[Nwmom]

My 3rd grader is doing a science fair project on extracting DNA from strawberries.

He got the idea after a science bus came to his school. I thought it was a little advanced, but he has
been reading about it, and he seems to understand the topic about as well as I do.

He wants to try extracting DNA from refrigerated strawberries and those left at room temperature to see which will
yield more.

He thinks it will be the refrigerated ones because the DNA will be more preserved.

I'm guessing it will be the ones at room temperature because their cell walls will be more broken down already.

Hubby thinks they may be the same since we're mashing them all up.
I'm not asking you to do the experiment for us here....what I'm hoping is that you can help me point my kiddo towards the right questions to ask, or resources. He has lots of books checked out on DNA as well as books describing this experiment. What I feel like he needs is a source that talks about what happens with cells as they age or fruit as it ripens??....maybe?? Is this making sense at all? He doesn't have to have a correct hypothesis in the end, of course, but I think he needs to have more information about Why that was his hypothesis. If anyone has any suggestions feel free to weigh in. Thanks in advance for your time. It's much appreciated.

[amyc]

Hi Nwmom - Have you taken a look at this project on the Science Buddies site:

Do-It-Yourself DNA
http://www.sciencebuddies.org/science-fair-projects/project_ideas/BioChem_p015.shtml?from=AAE

Objective: In this experiment, you will design a DNA Extraction Kit and use it to purify DNA from strawberries.

It sounds like your son is probably doing an experiment similar to this. You may find that the background and introductory information here are helpful, as are some of the "questions" provided that are considered important in doing this project. The step by step Experimental Procedure may also help as your son devises his project.

Please post any follow-up questions here. Our team of Experts are happy to assist!
Amy
Science Buddies

[robertpak]

Hi Nwmom.

It is great that you are exposing your child to the wonders of science.

So I see your project as either the "effect of strawberry temperature on DNA extraction yield" or the "effect of ripening on DNA extraction yield."

Temp:
You have the right idea of testing different condition to see how it affects the yield of DNA. Temperature is not going to change the amount of DNA in a strawberry, that is constant. But temperature could affect the extraction of the the DNA. If you read the link that Amy provided, you will see the procedures do not say if the strawberry should be chilled, room temperature or hot. You guys could be the first to determine if it makes a difference or not.

Ripening:
Ripening is a bit more advance of a topic and harder to control than temperature. It would be cool to see if ripening affects the yield of DNA extraction. Ripened fruit undergoes a lot of chemical changes that would affect the DNA yield, but most notably is that the ripened fruit will be less acidic.

Here is an interesting article for more reading on ripening
http://www.scientificamerican.com/artic ... t-ripening

Constant weight per trial:
You will need to run multiple trials for your experiment. In each trial you need to make certain that you are using the same amount of strawberry in each trial. This is especially important since you are testing the yield.

So tin a nutshell, this experiment is an investigation of conditions that yield more DNA.

Parting words: It is important that your child understands that the amount of DNA in a strawberry does not change from temp. or ripening. The gene expression do change in ripened fruit (which can be tested thru gel electrophoresis, but that is a bit more advance).

Best Wishes!

Bob