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Hi to all of you out there who use the Science Focus books, specifically Book 4. We have just done the DNA extraction prac with wheat germ. In the past we have had success with other methods using onions, lentils and blenders which are quite messy so this year the teachers decided to go with the one in the book. The first class to do it got fluffy-looking DNA using metho instead of pure ethanol, (because we were nearly out of ethanol and I was being tight) so for the second class to do it I got out the ethanol and they still got the same... Thinking the kids couldn't follow instructions (some groups had 2 or 3 starts cos they'd made mistakes) I tried it out myself so they could actually see the DNA strands and look at them under a microscope, which was the original intent of the prac anyway. Well, mine failed too!! So I can't blame the kids... Has anyone else tried this specific prac? I think we will go back to the messier ones next year.

Hi Rosalie,

We used to do wheatgerm, but now do one using kiwi fruit - the teacher does the first pasrt as a dem, then the students do the final bit, pouring ethanol down the side of a test-tube onto the mashed fruit. Quick, easy, mess-free, and best of all - fast wash-up!

Can send you the prac, if you like.

Sure sounds like a dream prac You can either post it here on chemtalk or email/fax to me murrayr@carinya.nsw.edu.au or 6762 1752. I'll have a look at it and see what the teachers think. I think it's a bit weird that the prac in the book doesn't work though so I'm curious to find out if others have had any success with that particular one.

I have never had any success with wheatgerm for DNA and now have one using banana which does work if the directions are followed properly.
It is a bit messy washing up though as you cant trust the kids to clean up mashed banana.
Wendy

We do DNA extraction using split peas. Very cheap and also use metho and works well. You do not have to even add the enzymes - whatever they suggested, either. Got lots of stringy stuff.

I have dissed the blender and now give students a ziplock bag with either strawberries or bananas in them. They mush it up in the bag. No mess and it gets thrown in bin at the end. I will attempt attach my procedure I think that as long as the ethanol or metho is really really cold and you pour it very slowly it dosen't matter which one you use.

If using wheatgerm it has to be "raw"wheatgerm............

We have been using the focus books for a couple of years and there are some dodgy experiments in them. I have kept a track of a couple and each year when we get up to them they are marked so we remember to do them differently. By memory I think even some of the morse codes in one of the levels are wrong.
Pearson education who are in charge of the writing and printing of them have asked me to let them know of any that we come across so that when they reprint they can change them, so if you have any suggestions I think they would be happy to hear from you.
Estelle.

We switched from wheatgerm to peas, but now everyone prefers the kiwi fruit idea. I think it was probably off chemtalk originally - if so, thankyou to whomever presented it first.
Much appreciated!

Hi all
We have always had success with the wheatgerm prac.with all our Yr.10 classes(135 in all!!) doing it. The secret is 'Raw Wheatgerm'!!! Also keep the metho in the freezer(doesn't have to be pure ethanol) The detergent needs to be a good one(I use palmolive green) I noticed Coles sell raw wheatgerm but you can also buy it at the healthfood store.
Hope this helps you
Cheers
Mother

Coming back to a very old topic... Wendy - do you use the same banana prac as nickyw? Or do you do the blender one? Or a different one?

DNA extraction seems to be relatively easy. I find that ripe banana (or frozen that has been defrosted) is best, but kiwi fruit or strawberries are also successful.

At a junior level, some classes put the fruit and all the other bits and pieces (detergent, salt etc) in a ZipLock back and squish is by hand, then sieve / filter.

I use the cheapest detergent possible (Homebrand) and have never had any issues.

I like banana because it makes the room smell nice (gotta love those esters...). Our Yr 12 Biology Prac manual uses onions which stinks up the whole place.

I successfully convinced our teachers to use banana using nickyw's method and I have never seen so much DNA!! I gave them 1/3 of a banana (they were fairly small bananas, too) per group. I made up the extraction buffer for them. Even the groups who messed up, broke their bags, forgot to add the extraction buffer so had to get their banana off the chux and back into their bags and can't measure accurately to save their lives got DNA out of it!!! I have suggested to the biology teacher that she might like to try it using the centrifuge to make it a little more 'scientific' (instead of filtering through chux cloths...). I really hope she tries it!

Phew...... Glad it worked.

Always get excellent results with bananas...well done.

Thanks for all those ideas. We still do the swishing of the mouth with gatorade prac with Yr 10 but I will certainly be suggesting these other alternatives.

nickyw, I was just looking at your strawberry method. How much meat tenderiser is it? 1 tsp or tbsp?
Thanks

1 teaspoon