DNA Extraction Lab Lesson Plan Information for Observation

Transcription

1 DNA Extraction Lab Lesson Plan Information for Observation Anna Drew Basic Unit Plan Outline/Overview Day One: Monday, March DNA Brainstorm: What students know about DNA, RNA, nucleic acids, and their importance/role 2. Begin DNA Notes: location of DNA in Prokaryotes & Eukaryotes; nucleic acids as monomers; structure of a nucleic acid; base pairing; Chargaff s rules; structure of a DNA molecule; DNA history 3. PBS Video: DNA structure 4. DNA Timeline Activity Day Two: Tuesday, March DNA Crystallography Lab 2. Amoeba Sisters Video: Structure and Function of DNA Day Three: Wednesday, March DNA Extraction Lab 2. DNA Packet: Model #1, Questions 1-10 Day Four: Thursday, March DNA Replication Notes: importance of DNA replication; location of DNA replication; enzymes involved; diagramming the DNA replication fork, direction of replication, and semiconservative strands 2. DNA Replication Modeling: students use plastic models to construct a strand of DNA, then replicate it. Use model to show instructor how the process occurs for a checkoff grade. 3. Textbook Work: students answer questions on p. 357 of textbook Day Five: Friday, March 17 (N.B. Anna is absent all day for a job fair in Radford. Left sub plans for CT) 1. DNA Packet: Model #2, Questions DNA Packet Review: go over Model #1 & #2 as review for quiz 3. DNA Quiz 4. Amoeba Sisters Video: Why RNA is just as cool as DNA 5. RNA Venn Diagram: students use a word bank to complete a Venn Diagram comparing DNA & RNA 6. Ch. 13 Bookwork: students complete a reading guide to accompany a textbook reading (Ch. 13, pp ) to introduce vocabulary regarding RNA & protein synthesis Day Six: Monday, March RNA & Protein Synthesis Notes: structure of RNA; types of RNA; codons; transcription & translation; location of protein synthesis; central dogma of microbiology 2. Our Room is a Cell Activity: students act as mrna molecules to retrieve DNA fragments from the nucleus and transcribe them into proteins at the ribosomes throughout the classroom Day 7: Tuesday, March Mutations Internet Search: students use their Chromebooks to research the answers to questions about varying types of mutations and the genetic diseases they can cause 2. DNA Packet: Model #3, Questions Day 8: Wednesday, March Mutations Notes: instructor goes over a presentation on mutations in order for students to look at their internet search page and add/correct information (their internet search will serve as their notes for this section of the unit) 2. In-class discussion/review: instructor will lead the students in a review of the broad concepts of the unit and how they connect to each other 3. DNA Review Worksheet: to be completed individually as test review No School Thursday PTC Day Day 9: Friday, March Go over DNA Review Worksheet: 5 minutes of review prior to test 2. DNA & RNA Unit Test: multiple choice exam 3. Introduce lesson on viruses: connect units to show how viruses are raw segments of DNA that are not technically alive

2 Day Three: Wednesday, March 15 A. Title: DNA Extraction Lab B. Purpose: Lesson Plan Outline Relevant VA Biology SOLs o BIO.1.e: conclusions are formed based on recorded quantitative and qualitative data o BIO.1.h: chemicals and equipment are used in a safe manner o BIO.5.g: the structure, function & replication of nucleic acids Relevant InTASC Standards o 3(d) The teacher manages the learning environment to actively and equitably engage learners by organizing, allocating, and coordinating the resources of time, space, and learners attention. o 3(e) The teacher uses a variety of methods to engage learners in evaluating the learning environment and collaborates with learners to make appropriate adjustments. o 7(a) The teacher individually and collaboratively selects and creates learning experiences that are appropriate for curriculum goals and content standards, and are relevant to learners. C. Materials Strawberries Bananas Ethyl alcohol or isopropyl alcohol, chilled DNA extraction buffer (salty, soapy water) Cheesecloth or coffee filters Funnels Graduated cylinders Glass stirring rods Ziplock bags 50 ml glass tubes/beakers Digital scales Safety goggles DNA extraction lab activity sheet D. Community Resources This lessons will be inherently engaging to the students by providing a hands-on, inquiry-based investigation into the composition of DNA. Students will be able to apply prior knowledge from the previous unit on Prokaryotic vs. Eukaryotic cells, and integrate that prior knowledge with the fact that the items from which we are extracting DNA are food items that they commonly encounter. E. Class Management and Safety Issues In this lab, we will be extracting DNA from samples of fruit. We will be using a basic, saline solution to break down the cellular structures of the fruit, and ethanol, a flammable alcohol, to precipitate the DNA molecules. Due to the nature of the chemicals being used, students are required to wear protective safety goggles for the duration of the lab. F. Procedures a. Engage (10 minutes): In this time, the instructor will introduce the concept of where DNA is located in Eukaryotic cells. She will ask the students what type of cells are Eukaryotes, and if fruits, such as those encountered in the lab, are classified as Eukaryotes. The students will then be introduced to the lab, and be informed that they will be extracting DNA from the nuclei of fruits. They will complete the pre-lab questions and read over background information in order to stimulate their curiosity and prior knowledge. b. Explore (30 minutes): The students will follow the procedure to extract DNA from fruit samples and measure the quantity of DNA extracted from each sample (in grams). This will allow the students to physically see DNA, and to get hands-on, inquiry-based experience to confirm that DNA is found in the nucleus of all Eukaryotic cells. c. Explain (20 minutes): The students will use their prior knowledge and their experimental data to answer post-lab questions on the activity sheet and to integrate this portion of the lesson with the unit as a whole. S G. Activity Sheets for Students (See below) H. Assessment: The lab worksheet will be collected and graded for completion and accuracy. The worksheet will count as a lab grade in the gradebook, and will be out of a total of 100 points. A scanned copy of the answer key/rubric is attached. Students will be awarded full or partial credit for each of the questions in the pre-lab, procedure, and post-lab sections.

3 Name: DNA Extraction Laboratory Background Information Deoxyribonucleic acid (DNA) is essential to the functioning of all organisms. It contains the information required to synthesize proteins, allowing organisms to build the proteins they need to survive and reproduce. DNA is located within the nucleus of the cell. It is stored in a de-condensed structure called chromatin. When the cell is about to reproduce, the chromatin condenses. This occurs when the long DNA molecules wind around histone proteins, tightly coiling to form compact, visible chromosomes. Different organisms have varying numbers in the copies of their chromosomes. Humans, for example, are diploid. This means that humans have two sets of chromosomes. Each set contains 23 chromosomes, meaning that humans have a total of 46 chromosomes. Purpose In this lab, students will extract DNA from strawberries & bananas, and will observe quantitative differences in the DNA of each type of fruit. A solution of soap, water, and salt will be used as an extraction buffer. The soap is a basic detergent, and functions to dissolve the phospholipid bilayers of the fruit cells. The salt causes chemical reactions that help break down the chains of proteins surrounding the nucleic acids. Once the cellular components are broken down, the DNA will be precipitated out of solution by adding ethanol. The colder the ethanol is, the less soluble the DNA will be, so the ethanol solution will be kept chilled. Pre-Lab Questions 1. What class of organic macromolecule includes DNA & RNA? 2. What is the monomer of DNA? Label the three parts of the DNA monomer. 3. Where is DNA found within eukaryotic cells? Will DNA be found in the same location in our fruit samples? Explain. 4. What is the basic shape of the DNA molecule?

4 5. On the diagram below, label the sugar/phosphate backbone, as well as the four bases. always bonds with cytosine. Thymine always bonds with. 6. Bananas are triploid, and have 11 chromosomes per set. How many total chromosomes do bananas have? 7. Strawberries are octaploid, and have 7 chromosomes per set. a. How many sets of chromosomes are found in an octaploid organism? b. How many total chromosomes do strawberries have? Safety Precautions In this lab, we will be extracting DNA from samples of fruit. We will be using a basic, saline solution to break down the cellular structures of the fruit, and ethanol, a flammable alcohol, to precipitate the DNA molecules. Due to the nature of the chemicals being used, students are required to wear protective safety goggles for the duration of the lab. Materials 1 strawberry 1 slice of banana Digital scale Coffee filters Funnel Ziplock bag (2) 50 ml glass tube (2) Glass stirring rod (2) 20 ml DNA extraction buffer 40 ml 70% ethanol

5 Procedure 1. Weigh your strawberry and record its mass (in grams) in Data Table Place your strawberry in a clean, empty Ziplock bag. Be sure that the bag is tightly sealed. 3. Use your fingers to mash the strawberry for about 2 minutes, or until the strawberry is ground into a pulp. 4. Add 10 ml of extraction buffer to the bag, and continue to mash the contents Data & Observations Hypothesis: Use this space to write a hypothesis about the DNA extraction do you think one type of fruit will contain more or less DNA than the other? Why? Data Table 1. Mass Measurements Strawberry Banana Initial mass (g) Mass of extracted DNA (g) Conclusion & Analysis 1. Why did you need to mash up the fruit? 2. The extraction buffer solution was added to the mashed-up fruit in order to dissolve membranes. What membranes was the solution dissolving? 3. Why did you need to filter the mashed-up fruit through the cheesecloth? 4. What was the purpose of adding the ethanol to the fruit? Why did the ethanol need to be cold? 5. What did the extracted DNA look like? Did it look like what you expected? Why or why not?

6 6. Calculate the ratio of DNA (g) to the initial mass of the fruit (g). Which type of fruit had a higher proportion of DNA? 7. Did your experimental data support or reject your hypothesis? Explain. 8. What is the relationship between chromosome number (ploidy) and the amount of extracted DNA? Is this a positive correlation, a negative correlation, or no correlation? How do you know? 9. The domesticated variety of bananas that humans breed and grow for consumption are triploid. How many sets of chromosomes are there in domestic bananas? 10. Wild-type bananas (those that have not been selectively bred by humans) are diploid. How many sets of chromosomes are there in wild-type bananas? 11. Do you think there would be more DNA extracted from domestic bananas or wild-type bananas? Explain. 12. Why might scientists need to extract DNA from an organism? List 2 reasons.