Can you do DNA extraction with strawberries without protease?

[Wervelwind]

I used to think you need protease but when I look up how other people have done this they say they don't use it.
I tried it myself this way:

- Put a large strawberry in a bag
- Mushed it for like 5 minutes
- Mixed 7g of salt, 14g of soap and 100ml of water in a beaker
- Added the strawberry bits into this, and mixed gently
- Filtered this
- Added 10 ml of this to a 25ml beaker
- Added 10 ml of cold ethanol from the side

Using a stirring rod, I was able to get something sticky but it's not solid and not the expected end result. I used a toothpick but that didn't do anything for me.

I was thinking of buying kiwis and putting it in a 60c waterbath for 15 minutes next time. Do you guys know if that will go better?

 

[Paul]

Fruit has proteases due to ripening so you don't need to add it, but it comes up on the exam so give them something labeled enzyme.

 

[Wervelwind]

Fruit has proteases due to ripening so you don't need to add it, but it comes up on the exam so give them something labeled enzyme.

Thanks. Do you know if there's anything else I can do that will give me good results?

 

[Paul]

Thanks. Do you know if there's anything else I can do that will give me good results?

you need to heat it for 20 minutes

1. Get a piece of fruit and chop it up
2. Put the pieces of fruit into the bottom of a small beaker and mash up carefully with a glass rod, next transfer the mashed up fruit to a boiling tube.
3. Add a spatula of salt and 2 fingers’ depth of washing up liquid to the boiling tube. Then half fill the boiling tube with water from the hot tap and mix
4. Leave the tube to stand in a beaker of water at 60oC for 10 minutes
5. While you are waiting, get a funnel and a piece of filter paper over another boiling tube
6. Drain the contents of your tube through the filter so that the green liquid goes into the clean boiling tube
7. Stand the boiling tube in a beaker of ice cubes for 5 minutes
8. Take the cooled tube to the teacher who will pour ice cold ethanol down the side of the tube. Your fruit DNA will float out of the mixture and you can fish it out

 

[Shazz]

I used to think you need protease but when I look up how other people have done this they say they don't use it.
I tried it myself this way:

- Put a large strawberry in a bag
- Mushed it for like 5 minutes
- Mixed 7g of salt, 14g of soap and 100ml of water in a beaker
- Added the strawberry bits into this, and mixed gently
- Filtered this
- Added 10 ml of this to a 25ml beaker
- Added 10 ml of cold ethanol from the side

Using a stirring rod, I was able to get something sticky but it's not solid and not the expected end result. I used a toothpick but that didn't do anything for me.

I was thinking of buying kiwis and putting it in a 60c waterbath for 15 minutes next time. Do you guys know if that will go better?

We do this but do put the soap/strawberry/salt mixture in a water bath at 60c for 15 mins. Filter into a 100ml beaker and add the ice cold IDA (ethanol) down the side of the beaker to form a 1cm depth ish layer. DNA is very visible as "snotty" layer within the top layer. Use wire hook to pull out a strand/globule. Works really well.

 

[seebee]

As Shazz, but no need to warm. Just filter after mushing with the salt/soap solution and add ice cold ethanol. Works well with Kiwi fruit too.

 

[TheRainbowTech]

We've found using a Kiwi Based Fruit smoothie and bottled Pineapple Juice for the protease works wonders! Less messy than crushing up the fruit too!

 

[Andrew Symonds]

Never bothered with it here just salty detergent water, and moderate heat in a water bath, the strawberry is now preferred as we have more than a few students with allergies to kiwi fruit.

 

[Wervelwind]

As Shazz, but no need to warm. Just filter after mushing with the salt/soap solution and add ice cold ethanol. Works well with Kiwi fruit too.

When I do it like that I can see the DNA as a white layer between the fruit solution and ethanol but can't pick up anything with a toothpick/paperclip

 

[Shazz]

When I do it like that I can see the DNA as a white layer between the fruit solution and ethanol but can't pick up anything with a toothpick/paperclip

I don't know why yours is like that. I give them plenty of strawberry each, chopped a bit but they chop/mash it more with a mortar and pestle. I give 3g salt , pre-weighed and they just add a good squirt of washing up liquid. Is you IDA ice cold- mine is in the freezer up until use? (I do think that strawberry works better than kiwi).

 

[Wervelwind]

I don't know why yours is like that. I give them plenty of strawberry each, chopped a bit but they chop/mash it more with a mortar and pestle. I give 3g salt , pre-weighed and they just add a good squirt of washing up liquid. Is you IDA ice cold- mine is in the freezer up until use? (I do think that strawberry works better than kiwi).

Yes it's ice cold. I give them 70% ethanol however instead of IDA but I don't think that should make a difference

 

[Wervelwind]

I'll give it one more go. Fingers crossed

 

[Wervelwind]

A dud again.

What I did this time:

- Mushed half a kiwi with mortal & pestle (after trialling yesterday with a kiwi, I cut one in half - one half was used yesterday and the other half I kept in the fridge and used it now)
- Made the extraction solution (7g salt, 14g dishwashing liquid and 125ml water). My dishwashing liquid expired 2 years ago but I don't know how relevant that is since loads of chemicals that expire can still be used
- Mixed both
- Put in 60c waterbath for 15min
- Filtered this after passing through muslin wire (perhaps I shouldn't have used this since it may have caught the DNA?)
- I ended up only using about 40ml of the filtrate since it takes forever to filter this even after passing the mixture through muslin
- Put the filtrate in a 100ml beaker, added a 1cm layer of ice cold ethanol

I didn't end up seeing anything or was able to pick up anything. Even compared to last time, I didn't even see a white layer inbetween. I have a strong suspicion that it's because of the muslin

This is doing my head in and the practical is in 2 hours. I'm just gonna give it since I can't think of anything else
Thanks guys

 

[Snailo]

The only obvious thing we do differently is use 95% ethanol (ice cold) and sit the beaker (boiling tube in our case) of filtrate in an ice water bath to cool it all down as well - it does need to sit for a little while once you've added the ethanol sometimes.

The washing up liquid we always use 'cheap' stuff, or water down the thicker stuff - it shouldn't be that much thicker than water.

We just use little sieves to filter it after its been in the water bath.

 

[Shazz]

A dud again.

What I did this time:

- Mushed half a kiwi with mortal & pestle (after trialling yesterday with a kiwi, I cut one in half - one half was used yesterday and the other half I kept in the fridge and used it now)
- Made the extraction solution (7g salt, 14g dishwashing liquid and 125ml water). My dishwashing liquid expired 2 years ago but I don't know how relevant that is since loads of chemicals that expire can still be used
- Mixed both
- Put in 60c waterbath for 15min
- Filtered this after passing through muslin wire (perhaps I shouldn't have used this since it may have caught the DNA?)
- I ended up only using about 40ml of the filtrate since it takes forever to filter this even after passing the mixture through muslin
- Put the filtrate in a 100ml beaker, added a 1cm layer of ice cold ethanol

I didn't end up seeing anything or was able to pick up anything. Even compared to last time, I didn't even see a white layer inbetween. I have a strong suspicion that it's because of the muslin

This is doing my head in and the practical is in 2 hours. I'm just gonna give it since I can't think of anything else
Thanks guys

Filter paper rather than muslin and we use the general one, and also strawberries are definitely better. We also only measure out 100ml of water, not sure if that it is a factor.

 

[Wervelwind]

Thanks. Gonna try it once more with an ice bath as well

 

[seebee]

Hello Wervelwind I use for the buffer 10ml washing up liquid, 90 ml water and 2g salt.
Add 10 ml to the squashed fruit in a bag.
Filter through filter paper to collect approximately 5ml of liquid - I use a boiling tube to collect.
Add ice cold ethanol - about 20 ml from ethanol kept in the freezer.
No need to warm or put in an ice bath.
Used this method today for a class and had good results.

 

[Wervelwind]

Hello Wervelwind I use for the buffer 10ml washing up liquid, 90 ml water and 2g salt.
Add 10 ml to the squashed fruit in a bag.
Filter through filter paper to collect approximately 5ml of liquid - I use a boiling tube to collect.
Add ice cold ethanol - about 20 ml from ethanol kept in the freezer.
No need to warm or put in an ice bath.
Used this method today for a class and had good results.

Thank you. What did you use to pick out the DNA? mounted needle?

 

[seebee]

Glass rod or wooden splint.

 

[Mad hatter]

I used to think you need protease but when I look up how other people have done this they say they don't use it.
I tried it myself this way:

- Put a large strawberry in a bag
- Mushed it for like 5 minutes
- Mixed 7g of salt, 14g of soap and 100ml of water in a beaker
- Added the strawberry bits into this, and mixed gently
- Filtered this
- Added 10 ml of this to a 25ml beaker
- Added 10 ml of cold ethanol from the side

Using a stirring rod, I was able to get something sticky but it's not solid and not the expected end result. I used a toothpick but that didn't do anything for me.

I was thinking of buying kiwis and putting it in a 60c waterbath for 15 minutes next time. Do you guys know if that will go better?

We do it in a similar way. We put the cut up strawberries in little sealable bags before the lesson ( they only need a small amount and you do not need as many strawberries if you do this) We use washing up liquid and salt water for the buffer. Fresh strawberries and kiwi work much better than frozen. We do not use water baths or heat it in any way. It always works if the fruit is fresh. It looks like long sticky strands when you lift if up from the surface with as stirring rod.