If you been teaching biology for a while, you know this lab well. If you are new to the scene, then let me introduce you to a must-do lab in biology. Yes; you do purify DNA in this lab using household materials.
I've put a spin on a classic lab, and aligned the DNA extraction lab with the Next Generation Science Standards (NGSS).
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This product is part of a Unit Bundle, which offers all you need to teach a Unit on DNA for students grades 7-12.
Get it here: DNA Unit Bundle
Do you want students to play the role of Watson and Crick in order to solve the structure of DNA? Click the link below to buy the NGSS Aligned: Race to Solve DNA Lab .
Get it here: NGSS Aligned: Race to Solve DNA Structure Lab
Materials and Setup: Generally, you will need frozen strawberries ( 1 per student or group), graduated cylinders, test tubes, beakers, cheese cloth, funnels, and consumables (soap, salt, water, etc.). One of the benefits of this lab is that I've converted much of it to an inquiry-based activity. For that reason, I advise letting students come up with their own materials and protocol to carry out the investigation.
For example, some might bring in a blender to break the cell wall, while others might use a meat tenderizer, or just their hand. Some might try soap or detergent to dissolve the cell membrane, while another group might want to try a solvent from home, or acetone.
Allow the students to make reasonable choices regarding the volumes they use of each ingredient.
I've even allowed students to try different foods (carrots, beans, etc.).
I also allow students to take risks/chances on substances that I am unsure will work. This is one of the hardest things for some teachers to do. If a student is comfortable with the possibility of not getting the expected result (and maybe not actually getting DNA purified), then let them experiment. The point of science is to test new ideas.
This being said, use your judgment for each class or group regarding how much help they may need arriving at reasonable choices. In my classes, I do not expect every group to be able to pick the right combo of ingredients. Many groups need prompting or Socratic questioning.