1. DNA Extraction Lab Introduction
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DNA Extraction Lab Introduction
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Biologists examine DNA from living things in many ways. DNA is inside the cell membrane of all cells, and in eukaryotic cells, it is further inside the double-layer nuclear membrane. To be studied, it must be extracted from the cell and nuclear membranes and separated from the histone proteins that coil it tightly into strands of chromatin.
Since DNA is so tiny and so tightly packaged in eukaryotic cells, it cannot be easily removed by physical forces alone. Instead, chemical processes and reactions are used, along with physical techniques.
In this lab, you will extract your own DNA from a saliva sample. Saliva contains white blood cells from your immune system, epithelial cells from your cheeks, gums and palate, prokaryotic cells from various eubacteria that live in and on our bodies and nucleic acids from viruses and the mitochondria in every human cell. You will extract DNA from all these sources in your saliva sample.
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2. DNA Extraction Lab Introduction
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DNA Extraction Lab Introduction
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To get the largest amount of DNA and the largest amount of human nuclear DNA, swirl your tongue around the inside of your cheek, gums and palate to gently remove cells into your saliva. Refrain from drinking any water, which would dilute the sample. Also, do not speak, since that dries your mouth and makes it harder to produce saliva. Deposit (spit) your saliva into the cup periodically, then move your tongue more to stimulate salivary glands to release more. The more saliva you deposit, the more DNA can be extracted. More DNA makes it easier to extract, and provides more material to examine.
In this lab, you will get to take your DNA sample home. You may choose to give your biological mother and / or father this DNA, since each of them contributed half of the DNA in the egg or sperm that combined to make the zygote that grew and developed into you.
DNA extraction is only the starting point for examining and working with DNA. One of the most common examinations is sequencing the DNA. Sequencing is determining the order of nucleotide bases in a gene, segment of DNA with instructions to make a protein, or in the entire genome.
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3. DNA Extraction Lab Procedures
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DNA Extraction Lab Procedures
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Immediately begin depositing saliva into the cup DO NOT INCLUDE MUCUS (PHLEGM) and sweep your tongue along cheeks, palate and gums to collect the most saliva and cells possible
Continue depositing saliva into your cup as you:
Read the lab procedures so you know what the next steps are
Read , outline and summarize the introduction
When you have covered the bottom of the cup and have collected as much saliva as possible, add a pinch of salt and gently swirl mixture until salt dissolves
Swirling salt helps physically separate cells from clumps, and chemically precipitates proteins and carbohydrates (causes them to separate from liquid into solids) that cause cells to clump. Separate cells are easier to extract DNA from
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4. DNA Extraction Lab Procedures
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DNA Extraction Lab Procedures
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Add 2 drops of detergent and swirl gently to mix (DO NOT shake or stir to make bubbles)
Detergent attracts phospholipids that make up the cell membrane and nuclear membrane that enclose the DNA. This attraction lyses (breaks apart) the cell and nuclear membrane, releasing DNA and other cell parts into the solution
Let the mixture stand for 5 minutes while you outline and summarize lab procedures
It takes time for the detergent to lyse the cell membrane and diffuse through the cell to lyse the nuclear membrane
Pour the mixture into the test tube (not more than 1 inch high)
Keep the remainder in cup until cleanup time
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5. DNA Extraction Lab Procedures
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DNA Extraction Lab Procedures
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The instructor will bring you a pinch of meat tenderizer. Swirl gently, since this will unwind the DNA from each cell into a long, fragile double helix. DO NOT shake or stir, since this will break up the strands into smaller pieces that are harder to collect.
Tenderizer is an enzyme that breaks down the tougher proteins, causing meat to soften. DNA is normally coiled around histone proteins (like thread around a spool) which are tightly coiled to form fibers of chromatin. The enzyme breaks down the proteins, unwinding the DNA into the very thin and fragile double helix.
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6. DNA Extraction Lab Procedures
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DNA Extraction Lab Procedures
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8. Slowly and carefully pipette an equal amount of isopropyl alcohol into your test tube on top of the mixture
DO NOT TOUCH THE TEST TUBE OR MIXTURE with pipette tip.
DO NOT PUT CONTAMINATED PIPETTE IN ALCOHOL
Alcohol is less dense than water, so will form a separate layer on top of the watery mixture if you place it in carefully. If it mixes, it will often float to the top after sitting still.
DNA has been released from the membranes and unwound from the proteins, but is mixed with other cell parts. DNA is less dense than water, so it will gradually float up as white strings into the alcohol layer
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7. DNA Extraction Lab Procedures
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DNA Extraction Lab Procedures
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Set the test tube in the rack while you continue outlining and summarizing procedures
Look for white strings in the lower alcohol layer, just above the watery layer. Use the stick provided to gently swirl those strings into one clump of DNA
Carefully pour the test tube contents into your paper cup, using the stick to keep the DNA clump in the tube
Open the eppendorf lid, then place the string in the hinge. Carefully pour the DNA clump into the eppie tube and close the lid. Congratulate yourself on a successful DNA extraction! Share it with the people that gave you your DNA!
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8. DNA Extraction Lab Conclusion
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DNA Extraction Lab Conclusion
Answer these questions with your best sentence skills, using information from introduction and procedures
What cells are you extracting DNA from in this lab?
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What is one of the most common examinations of DNA?
Why do we add salt?
Why do we add detergent?
Why do we add the meat tenderizer?
Why do we add alcohol?
Where did your DNA orginally come from?