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I attempted to address several problems in this project. 

Do different DNA sources yield different amounts of DNA?

Different DNA sources produced different amounts of DNA. . Molecules can interfere with DNA extraction, they bind to the DNA and prevent the DNA from precipitating. Where a lot of DNA is extracted, there are fewer interfering substances. The same DNA source produced different amounts in each test tube. The amount of DNA extracted depends on the source: number of cells, age, freshness, and water content. Too much water added to the source, or if the source has a high water content yields less DNA.

Do different parts of a plant affect the amount of DNA extracted?

Different plant parts produced different amounts of DNA. From the leek, the leaves produced the most DNA, the bulb part produced the next highest amount, and the roots yielded no DNA. The roots are mostly starch because they produce food for the plant.

Do changes in the protocol affect the amount of DNA extracted? 

 Changes in the protocol affected the amount of DNA produced.


The unstrained kiwi yielded less DNA than the strained kiwi.


The colder the alcohol, the more DNA was extracted. The colder the alcohol, the faster the DNA was precipitated. Colder alcohol is less dense than water, and less dense than warmer alcohol.


The addition of meat tenderizer yielded less DNA but it was supposed to yield more. Maybe it was stirred too much and the DNA broke up, or there was an error in mixing the source. Parsnip yielded the most in Experiment 1, least in Experiment 4 but I remember it wasnít as pulpy in Experiment 4.


The protocol designed for wheat germ yielded DNA. When using wheat germ (ground & unground) in the other protocol, no DNA was produced.


The protocol amounts were doubled for the change in protocol for the 4.5 degree C, 21.5 degree C and the meat tenderizer. Generally less DNA  was extracted overall when amounts were doubled (ex. Parsnip produced least DNA and the meat tenderizer did not work the way it was supposed to).


Do different DNA sources require different protocols?

 The protocol designed for wheat germ yielded DNA. When using wheat germ (ground & unground) in the other protocol, no DNA was produced.



Why did my results vary? 

Results probably vary because it was difficult to measure everything exactly and do everything exactly the same. Some examples of experimental error:  some of the meat tenderizer stuck to the inside of the test tube and didnít reach the source, inconsistent tilting of the test tube when pouring in alcohol, forgetting to tilt the test tube, not pouring the alcohol slow enough, not putting enough of an ingredient in or too much, DNA could leak through the sieve when weighing, it was something difficult to remove all the DNA from the source to weigh it, accidentally bumping a test tube.


Many DNA extraction experiments give approximate amounts, not exact amounts so maybe exact amounts arenít crucial. I found one lab that required equal amounts of water and DNA source. The lab I used had twice as much water as DNA source.


This experiment should be repeated several times. This experiment produced some unexpected results (ex. Meat tenderizer didnít produce more DNA). Sometime science is hard to do, it can be fun and tedious, canít be careless.


Next Time ...

I would like to know what would happen if I would dehydrate all the sources so I would be using exact source amounts. If I had access to equipment, I would like to be able to centrifuge and use a gel electrophoresis.


If I was a science teacher and I was going to do a DNA extraction lab I would use cranberries (produced a lot, nice color), all parts of the leeks to show the difference in plants, and the onions and peas looked the most unique (stringy). I would also do a wheat germ DNA extraction because the strands are long and stringy across the top of the alcohol. I would also get them to compare different protocols.