понедельник, 23 октября 2017 г.

DNA Extraction Lab. 9th Grade

Before you start writing lab report some necessary tips
Whole Lab Report has to be written in PAST tense
There are Title, Purpose, Equipment, Procedure, Result, Conclusion stages which you can't ignore
There is SAMPLE Lab Report which could give you much inside in what you have to do to get the best grade
Title: DNA Extraction
Purpose: To extract DNA from onion cells by using special simple techniques. To understand the role of each step of the work in getting DNA from the cell nucleus. To improve verification skills by communicating with classmates.
Equipment: onions, table salt, cold water, liquid detergent, isobutyl or ethyl alcohol with the toluene in it.

First, you need to find something that contains DNA. Since DNA is the blueprint for life, everything living contains DNA.
Step 1: Slice the plant into many tiny pieces.
1/2 cup of split plant (100ml) 
1-2 teaspoons of table salt 
1/4 of cup of cold water.
So you now have a really thin plant-cell soup. 
Step 2: Soapy mass.
Pour your thin plant-cell soup through a strainer into another container (like a measuring cup) or leave it in the same cup. Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix.
Answer this: Why detergent? How does detergent work? Think about why you use soap to wash dishes or your hands. After adding the detergent, what do you have in your plant soup?
Let the mixture sit for 5-10 minutes. Pour the mixture into test tubes, beakers or other small glass containers, each about 1/2 full.
Step 3: Alcohol Separation and so on.
DNA is a long, stringy molecule
Tilt your test tube and slowly pour rubbing alcohol (70-95% isobutyl or ethyl alcohol with the toluene in it) into the tube down the side so that it forms a layer on top of the plant mixture. Pour until you have about the same amount of alcohol in the tube as plant mixture.
Alcohol is less dense than water, so it floats on top. Look for clumps of white stringy stuff where the water and alcohol layers meet.
DNA is a long, stringy molecule. The salt that you added in step one helps it stick together and suck out cytoplasm with all inner stuff from the cell. So what you see are clumps of tangled DNA molecules! 
DNA normally stays dissolved in water, but when salty DNA comes in contact with alcohol it becomes undissolved. This is called precipitation. The physical force of the DNA clumping together as it precipitates pulls more strands along with it as it rises into the alcohol.
Conclusion: Make sure you write usual conclusion using results. Then answer questions:
1. What can I do to increase my yield of DNA?
2. Why add salt? What is its purpose?
3. Why is cold water better than warm water for extracting DNA?
4. How is the cell wall of plant cells broken down?
5. How can we confirm the white, stringy stuff is DNA?
You can use a wooden stick or a straw to collect the DNA. If you want to save your DNA, you can transfer it to a small container filled with alcohol.

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