bicenten Extracting DNA from Plants The cells of different organisms contain different amounts of DNA. The size of the g

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Bicenten Extracting Dna From Plants The Cells Of Different Organisms Contain Different Amounts Of Dna The Size Of The G 1 (75.57 KiB) Viewed 142 times

Bicenten Extracting Dna From Plants The Cells Of Different Organisms Contain Different Amounts Of Dna The Size Of The G 2 (95.19 KiB) Viewed 142 times

bicenten Extracting DNA from Plants The cells of different organisms contain different amounts of DNA. The size of the genome, the number of chromosomes. and the number of copies of each chromosome within a cell influence the amount of DNA that the cell contains. Determining the DNA content of a single cell is difficult. However, estimating the DNA content of a given mass of cells is possible. In this investigation, you will compare the amount of DNA extracted from different plant species Testable Question Do all plant species contain the same amount of DNA per gram? Prediction Conduct online research to determine the somatic cell will chromosome number for each plant species that you t use in this investigation. If possible, find the genome size in base pairs. Based on your findings, predict which plant species will contain the greatest amount of DNA per gram. Variables What are the dependent and independent variables in this investigation? Which variables are held constant? Experimental Design You will extract DNA from three plant species: strawberry, kiwi, and onion. You will dry the DNA and record its mass for each species. You will then calculate the percent yield of DNA, per gram of original plant tissue, and compare this yield for the different samples. SAT HANDBOOK Equipment and Materials safety goggles • lab apron • rubber gloves balance. mortar and pestle . 4 large test tubes • 3 graduated cylinders (10 ml) e glass rod • hot plate . 4 . . CONTROLLED EXPERIMENT Questioning Researching od Predicting ring clamp utility stand thermometer 2 large beakers Planning -Observing Controlling Analyzing Variables Evaluating Performing Communicating test-tube holder funnel 50 ml. graduated cylinder . forceps, hook, or paper clip .strawberries 0.9 % w/v solution of sodium chloride, NaCl 10% w/v solution of sodium dodecyl sulphate. (SDS, or liquid soap) water. - ice cheesecloth or filter paper. • meat tenderizer solution 6 % w/v (3 g/50 ml. of solution) 95 % ethanol (very cold) paper towels onions To unplug the hot plaie, pull on the plug, not on the cord Do not touch the top of the hot plate. It may be hot even if it does not appear to be hot. If you are hosting a beaker on the hot plate, make sure that you surround it with a ring clamp secured to a utility stand. Alcohol is flammable. Make sure that there are no open llames nearby. Procedure SKILLS VANDBOOK A2.2 1. Put on your safety goggles, lab apron, and rubber gloves. 2. Obtain approximately 10 g of strawberries. 3. Place the strawberries in the mortar, and crush them using the pestle. This will separate and crush many of the cells, helping to expose the DNA. 4. Determine the mass of a large test tube. Transfer the crushed strawberries to the test tube, and determine the mass of the strawberries and test tube. 5. Add 10 mL of 0.9 % NaCl solution to the test tube. Mix well with a glass rod. Positive charges from Na will neutralize the negative charges on the DNA, prevent the DNA molecules from repelling each other, and help to separate the DNA from the histone proteins. Chapter 6 investigations 299 • kiwis
6. Add 3 mL of 10 % SDS solution (soap), and mix Analyze and Evaluate thoroughly for 30s with a glass rod. The soap will break down the plasma membranes, further exposing the DNA. (a) What is the purpose of mashing up the strawberries, kiwis, and onions? (b) What proteins associated with DNA might be broken down by the meat tenderizer? 7. Place the test tube containing the mixture in a 60 °C hot-water bath for 10 min. The high temperature will break down the cell walls and cell membranes, and help to denature any enzymes that could degrade the DNA. (c) Since DNA precipitates out in ethanol, is DNA soluble or insoluble in ethanol? Explain. 8. Using a test-tube holder, transfer the test tube into an ice-water bath for 5 min. (d) How could the haploid, diploid, or polyploidy nature. of the chromosomes of a plant affect the percent yield. of DNA? 9. Strain the strawberry mixture through a piece of cheesecloth or filter paper, into a beaker, to remove any remaining solids. (e) Compare the percent yield of DNA from the strawberry, kiwi, and onion tissue samples. Do your results support your prediction? Also compare your results with the number of chromosomes or genome size of each of these species. 10. Add an amount of meat tenderizer solution that is equal to half the volume of your filtrate. Swirl to mix. The meat tenderizer will break down any proteins that are still attached to the DNA. (f) Is the DNA that you extracted pure? Why or why not? If not, what other macromolecules might be present your DNA sample? in 11. Pour the mixture into a large test tube. Measure a volume of ice-cold ethanol that is twice the volume of your mixture. While holding the large test tube on a slant, very slowly pour the ethanol down the inside wall of the test tube. The alcohol will form a transparent layer on top of the mixture. (g) Provide additional reasons for a difference in the percent yields of DNA for the three types of plant tissue. (You should conduct research, as well as providing your own reasons based on your observations). Hint: How would cell size or water content affect the DNA yield? Apply and Extend 12. The DNA will begin to precipitate out of the mixture and aggregate where it contacts the chilled ethanol. It is a white, jelly-like substance. Using a glass rod. gently twirl the DNA that has precipitated out of the ethanol, and remove it from your mixture with forceps, a hook, or a bent paper clip.. (h) Research different plants and animals and find out the size of their genomes. Would you describe genomes as being relatively similar in size or highly variable? Support your answer with examples. 13. Determine the mass of a small piece of paper towel. Place the jelly-like DNA extract on the paper towel to dry overnight. (1) Would you expect fresh peas or dried peas to provide a higher yield of DNA per gram? Explain. (j) 14. Repeat Steps 1 to 13 with the kiwis and the onions.. 15. Once the samples are dry, record the combined mass of the paper towel and DNA extract for each of the three samples. Determine the mass of the DNA extract. 16. Calculate the percent yield of DNA from your original plant tissue samples. The amount of DNA can be better quantified by using a spectrophotometer. Research how a spectrophotometer works and how it can be used to determine the amount of DNA in a sample. WEB LINK