DNA (Deoxyribose Nucleic Acid) is a nucleic acid that has many names, each representing the phases that it undergoes (chromosomes, chromatin, genes/alleles); it resides in the nucleus (bound by 2 *phospholipid bilayers) of almost every cell in the body (red blood cells being an exception). DNA (your genotype) is double stranded and is responsible for replicating (from 46 to 92) during Interphase, so that mitosis can make new cells, repairing and allowing for growth in the body. It is also responsible for transcription and translation, a series of processes that allows for the genotype to become a phenotype (what you look like and metabolic processes). DNA is ~ 2 M long, and yet fits into a cell that is ~ 100 µM in size! Simple household solutions, based on their chemical properties (polarity) are used to extract DNA for examination. Once DNA is extracted from the nucleus (nuclear envelope) it can be examined in many laboratory tests for a variety of reasons: DNA quantification, DNA fingerprinting, Real-Time PCR analysis, genetics testing and genetic therapy. In this lab basic household chemicals are used to extract DNA by *precipitating it; reflecting on basic chemistry (the early chapters in the text) will assist in understanding why salt, soap and alcohol are used. Consider what type of chemical each is, including DNA; consider what *charges each hold and their solubility, not to just the DNA, but to each other. As you perform this lab, contemplate what each chemical is doing as they interact. Key words are marked with an *.
Participant's name (student):
Review basic chemistry by extracting DNA from your check cells. Materials
Obtain the materials needed as you perform the procedures/lab: •
Sports drink (Gatorade, Powerade, Propel, etc.)
Graduated cylinder (small)
Lysis Solution (5 mL)
Plastic test tube w/cap
Test tube rack
95% Ethanol (Refrigerated Ethyl alcohol)
Locate a test tube and label the tube with your initials using a marker. 2.
Locate a small cup, funnel, and sports drink.
Using (~ = approx) ~20 mL of the sports drink, swish it around in your mouth for 1 full minute. Note: As you swish the liquid around, gently and continuously scrape/bite one the sides of your cheeks with your teeth to help release cheek cells into the drink. 4.
Gently spit the sports drink (that now contains your cheek cells) into the small cup. 5.
Using the labeled test tube and the funnel, swirl then pour the contents of the cup into the labeled test tube until it is ½ full. Discard any remaining liquid in the cup into the sink, and throw the cup away. 6.
Locate the lysis solution (contains salt, soap and dist H2O); holding the test tube at a slight angle, use the graduated cylinder to add 2 ml of the lysis solution to the collected cheek cells. 7.
Cap the test tube properly (a tight seal), and invert it 5-8 times. This inverting mixes the lysis solution with the cheek cells. 8.
Place the test tube in the test tube rack, and allow the solution to stand for about 2-3 minutes. 9.
After 2-3 minutes, describe what is observed in the test tube under question #1 in the evaluation section. 10.
Locate the cold alcohol (refrigerator). Do not leave the alcohol out in room temperature. 11.
Using the graduated cylinder, pour the cold alcohol to the test tube by holding the test tube at an angle, letting the alcohol run gently and slowly down the side of the test tube. Do not mix the cheek cell solution with the alcohol. Note: add the alcohol until the tube is almost full. There should be 2 distinct layers once the alcohol is added. Gently place the test tube back in the test tube rack, do not shake or disturb the solutions. 12.
Observe and describe under question #2, as the two layers (cheek cells and the alcohol) begin to converge. 13.
Let the test tube stand undisturbed for 15 minutes, the DNA will precipitate...
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