Does freezing prevent DNA extraction? Background Generally, the freezing process is damaging to cells. As cells freeze, ice crystals form which puncture cell membranes releasing their contents....

Lab Report: how do you think freezing affects the extraction of DNA?



Does freezing prevent DNA extraction? Background Generally, the freezing process is damaging to cells. As cells freeze, ice crystals form which puncture cell membranes releasing their contents. Freezing and preserving biological specimens is an important need in many research and medical applications and consequently the effects of freezing on cells and molecules of cells is an important area of investigation. Here, the question is whether or not the freezing process damages DNA and interferes with the ability to extract DNA from samples. Available materials ● frozen and fresh strawberries ● dish soap ● test tubes and racks ● salt ● Sandwich bags ● paper towel ● 91% Isopropyl Alcohol ● Beakers ● Graduated cylinders ● pipets Special instructions DNA extraction: ● First make up a DNA lysis buffer solution by mixing 45ml of deionized water, 5ml of dish soap, and 1g of table salt. ● Mash up the strawberries in the sandwich bags, be sure to keep the frozen and fresh separate. ● To the sandwich bag add 12ml of the DNA lysis buffer solution and mix to combine ● Use a filter paper to filter out the strawberry/solution mixtures into clean beakers ● Once you have the filtered solutions, transfer them to separate test tubes ● To each of the test tubes add approximately 10ml of cold 91%isopropyl alcohol. Tilt the tube and gently pour the alcohol down the side into the tube. ​You do not want the alcohol to mix with the strawberry solution; rather you want it to form a separate layer on top of the strawberry solution. If easier, feel free to use a pipet to add the alcohol. ● Wait approximately 5 minutes, if DNA is present it should precipitate as a white stringy material between the alcohol and strawberry solution layers. Once precipitated, you can pull it out with a stir rod and examine it under a microscope if interested. 63 Lab tips ● Again, the most important point in the procedure above is to not allow the alcohol and strawberry solution layers to mix. Gently and slowly add the alcohol so that it forms a layer above the strawberry solution. Questions to consider: ● What is DNA? Why is it important? ● Given the ingredients of the DNA lysis buffer solution, how do you think it facilitates the extraction of DNA? ● Strawberries are polyploid and may have up to 8 sets of chromosomes. How might this help or hinder the ability to extract DNA? ● What sorts of technologies or medical procedures are dependent on freezing cells or DNA samples? Hypothesis check (write down and have your instructor check your hypothesis before proceeding to your experiment): 64 Names:_______________________________________________________________________________ Report Title:___________________________________________________________________________ Introduction: 65 Methods: 66 Results: 67 Discussion: 68 Names:______________________________________________________________________________ R​EPORT​ R​UBRIC​ (15​PTS​) Attach this rubric to the back of your lab report. I​TEM​ D​ESCRIPTION​ (​EACH​ ​ITEM​ ​IS​ ​WORTH​ 1 ​POINT​) P​OINTS​ E​ARNED Introduction 1 1/2 0 1 Introduction provides sufficient explanation/background material to justify hypothesis 2 Hypothesis is correctly stated Methods 3 Methods are appropriate and correct for hypothesis 4 Experimental and control groups are clearly identified 5 Methods are complete, and accurately describe investigation performed Results 6 Trends/patterns observed are clearly stated. 7 Graphs and/or tables are correct and illustrate information clearly 8 Graphs and/or tables are correctly formatted and captioned 9 Graphs and/or tables are referenced correctly in the text Discussion 10 Hypothesis is clearly addressed and conclusions are valid 11 Potential experimental limitations are discussed 12 Broader implications and take-home message are clearly stated Overall 13 Report addresses one or more of the “Questions to consider” at a relevant point in the report (usually, somewhere in the introduction, methods, or discussion depending on the question) 14 Report is clear, logical, and easy to follow 15 Report has correct spelling and grammar Bonus! 16 Report correctly cites and incorporates textbook or other appropriate scientific resource (not Wikipedia or other science website unless approved by instructor) Total: 69
Jun 19, 2021
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