DNA Necklaces Pre-Lab
BACKGROUND: Deoxyribonucleic acid (DNA) is the genetic material present in all cells that contain the instructions for how to make you, YOU!
By now, you know that a single monomer of DNA is called a nucleotide. A nucleotide consists of 3 parts: a phosphate group, a sugar, and a nitrogen base. Hundreds of thousands of nucleotides are hooked together to form a chain, and two chains are paired together and twisted into a double helix to form the finished DNA molecule. In eukaryotes, such as humans, DNA is wrapped around proteins, called histones, creating structures called chromatin. Chromatin is contained in the eukaryote’s nucleus.
PURPOSE: In this activity, we will be taking a look at the DNA in your cheek cells. You will be able to collect your cheek cells by swishing a liquid around your mouth. Very pure DNA can be easily extracted (taken out) from cells in a research laboratory, and somewhat less pure DNA can be extracted with some simple techniques. This is what you will be doing.
PROCEDURE: We will add detergent to separate the phospholipids in the cell membranes and the membranes that surround the nucleus (the nuclear membrane). DNA is now free to leave the nucleus. In the last part of the lab, we will add isopropyl alcohol. DNA clumps together in alcohol because it is insoluble in alcohol. When molecules dissolve in a solution, the molecules are soluble, and you would not be able to see it. In this case, we need to add the alcohol so that the DNA molecules will become insoluble and become visible.
PRE-LAB QUESTIONS:
Before you complete the lab, answer the following questions.
1. What is DNA?
2. Describe the shape of DNA.
3. The monomer of DNA is called a ______.
4. What are the three parts of a nucleotide?
1) 2) 3)
5. What is chromatin?
6. What kind of cells will you be using to extract DNA?
7. Fill in the chart below to indicate what two things we will be adding to the cells to extract DNA and what each does.
Substance Added to Cells / Why do we use it? / What does it do?1.
2.
Teacher Signature
DNA Necklaces!
BACKGROUND: Deoxyribonucleic acid (DNA) is the genetic material present in all cells, from bacteria to humans. In this activity, we will be taking a look at the DNA in your cheek cells. You will be using the same basic steps that biologists use when they extract DNA (e.g., to clone DNA, to make DNA fingerprints).
You will follow these 3 steps to take out your DNA:
Detergent
eNzymes
Alcohol
MATERIALS:
§ Small cup of Swish Liquid (1 per student)
§ Graduated test tube (1 per student)
§ Microtube (1 per student)
§ Tube rack (1 per group)
§ Toothpicks (1 per student)
§ Pipettes
§ Detergent solution
§ Isopropyl alcohol (ice cold)
§ Materials to make necklaces
PROCEDURES:
Getting Your Cells
1. Swish the Swish Liquid in your mouth for 60 seconds. Have your Resource Manager time you.
NOTE: The harder you swish, the more cells you will be getting—therefore more DNA.
2. Spit your Swish Liquid back into your cup.
3. Pour the Swish Liquid into the graduated test tube until the test tube is halfway full (about 5 mL).
4. Throw away your cup.
Breaking Down Your Cells
5. Using a dropper, add 1 mL of the detergent solution to your test tube. Cap the test tube TIGHTLY. Gently mix the contents by turning the tube upside down and right-side up several times.
NOTE: Do this slowly so that you do not make too many bubbles.
6. Uncap the test tube, and place it in the tube rack (remember which one is yours!). Send your Resource Manager with the tube rack to your instructor for the alcohol. Your teacher will add 4mL of alcohol into each test tube.
Getting Your DNA
7. Wait for the DNA to start forming clumps.
NOTE: This will take a few minutes. Do not stir or shake the tube.
8. Using a toothpick, gently twirl it through the white clumps at the top of the test tube (this is called “spooling”. Carefully lift up the toothpick to see the DNA you have extracted!
Making Your Necklace
9. Using the toothpick, put your DNA into a microtube.
10. Have your instructor fill the test tube with isopropyl alcohol. Seal the microtube tightly.
11. CLEAN UP! Rise your test tube and place it back in your rack. Throw away cups and toothpicks. Wash your hands with soap and water.
12. WHEN YOU ARE DONE CLEANING UP: Create your DNA necklace!
Check Your Understanding!
1. On the back, describe the basic structure of DNA. Use the words: double helix, nucleotide, monomer, and nitrogen bases.
2. How is DNA stored in the nucleus?
3. Complete the chart below to show the steps you followed to extract the DNA from your cheek. Below each step, include WHY you did what you did. Some have already been filled in for you.
4. On the back: If your DNA is what makes you, YOU, what part of YOUR DNA makes you unique? How is your DNA different from someone else’s DNA? How is it the same?
Check Your Understanding!
1. On the back, describe the basic structure of DNA. Use the words: double helix, nucleotide, monomer, and nitrogen bases.
2. How is DNA stored in the nucleus?
3. Complete the chart below to show the steps you followed to extract the DNA from your cheek. Below each step, include WHY you did what you did. Some have already been filled in for you.
4. On the back: If your DNA is what makes you, YOU, what part of YOUR DNA makes you unique? How is your DNA different from someone else’s DNA? How is it the same?