DNA, or deoxyribonucleic acid, is the building block of life. Nearly all living creatures, from microscopic bacteria to massive California Redwoods to humans, have DNA in their cells. Just like a book, DNA is constructed of "words" and "letters." However, for many students, it can be hard to picture DNA, since you can't see its structure with the naked eye.
DNA Basics
DNA is the genetic code for life. It is found in almost all living creatures in the nucleus of the cell. DNA contains only four letters: A, G, C, and T. Each letter is a chemical base that pairs up with another to create the iconic double helix that is DNA. Adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G) to create base pairs. Each base pair also attaches to a sugar molecule and a phosphate molecule to create a nucleotide, or a "word." Nucleotides then arrange themselves into long strands that form a ladder shape called a double helix.
Students start learning about biology and DNA as early as 5th and 6th grade in the United States. A great way to teach students of all ages about DNA is through models. You, of course, can purchase a kit to make a model, but homemade models are just as fun and a lot cheaper.
Edible DNA
Young students are just learning about biology so it's best to keep these models as simple as possible. This model uses candy to symbolize the basic molecules and structure of DNA. This project will take about an hour and is best for students in grades four through six.
Materials:
- Colored marshmallows (or alternative multi-colored soft candy like gumdrops)
- Licorice ropes
- Toothpicks
Instructions:
- Assign each color marshmallow a base (e.g. pink is A, white is T).
- Pair appropriate colored marshmallows together.
- Place one of each pair of marshmallows on the end of a toothpick.
- Stick each end of the toothpick with marshmallows into a licorice rope.
- Continue until the entire string of licorice has toothpicks with base pairs.
- Hold one end of the licorice rope and twist to form the double helix.
- Enjoy the edible DNA structure.
Styrofoam DNA
Middle school students have begun to understand the basics of biology and can learn more about DNA's unique structure. This model goes into a bit more depth with the sugar and phosphate backbone of the DNA structure. This project should take two hours of class time, in two separate classes, and is appropriate for grades seven through eight.
Materials:
- 100 small one- to two-inch styrofoam balls
- Toothpicks
- Six different paint colors
- Paint brushes
- Glue
Instructions:
- Choose different paint colors for the sugar molecules, phosphate molecules, and each of the four bases.
- Paint 20 balls as the sugar molecules and 20 balls as the phosphate molecules.
- Paint 15 balls for each base with their appropriate color.
- Let styrofoam balls dry.
- Once the styrofoam balls are dry, pair bases together (A to T, C to G).
- Stick toothpicks between each base pair.
- Glue toothpicks and styrofoam balls as needed.
- Create two sugar and phosphate backbones by using a needle and thread and threading the balls together.
- Attach base pairs to the sugar molecule with their toothpicks.
- Rotate the styrofoam balls as you add base pairs to create the twist in the double helix.
Twelve Base Pair DNA Model
High school students should understand the basics of DNA, genetics and cell division. At this point, students should also have some basic understanding of chemistry and chemical bonds. This model shows the chemical structure of DNA. Students build models of adenine (A), thymine (T), cytosine (C) and guanine (G). Then they pair the adenine with the thymine, the cytosine with the guanine and create a realistic model of DNA.
Materials:
Instructions:
- Take one medium styrofoam ball and insert a toothpick. Paint the ball and then insert the ball into the flat styrofoam piece to dry. Paint all your styrofoam balls in the same manner and leave them there until they are dry. To make one base pair (you'll want 12):
- Paint four balls one color to represent phosphorus
- Paint 26 balls one color to represent oxygen
- Paint 17 balls another color to represent nitrogen
- Paint 30 balls a different color to represent carbon
- Leave the smaller white balls as is; they represent sugar.
- Let styrofoam balls dry.
- Leave the smaller styrofoam balls plain as they represent hydrogen bonds.
- Cut toothpicks to the appropriate lengths (based on the bond distances) to make the bonds.
- Create the molecules with toothpicks inserted at the appropriate places. You will need your DNA structure diagram.
- Use glue to attach the toothpicks to the styrofoam balls as necessary.
- Create two sugar and phosphate backbones by stringing sugar and phosphate balls (20 balls each side) using a needle and string.
- Attach base pairs to the sugar molecules by sticking toothpicks on the opposite side of each base pair.
- As you go, create a helix shape so that the finished product looks like real DNA.
DNA Models for Visual Learners
DNA, genetics, and biology as a whole are taught to students from a young age. However, many students may have a hard time grasping the concept if they are visual learners. Models are a great way to help young minds understand one of the most important science topics.
