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Science - 5th Grade
Standard 5 Objective 1
1 class periods of 60 minutes each
Students extract DNA from wheat germ. This is a quick and low cost experiment for extracting very observable quantities of DNA. Students can each take a small amount of DNA home. Students also make a model of DNA out of licorice and marshmallows.
Traits are observable characteristics that are passed down from parent to child. For example; hair color, eye color and height are traits. These traits are passed down from parent to offspring through a chemical called deoxyribonucleic acid or DNA. Our individual combinations of traits makes us all unique.
DNA is found in the nucleus of every cell of our body and every cell of any living thing. We have a lot of DNA. The basic structure of DNA is the same in every living organism it just differs in the order of its code.
DNA provides the instruction or blueprint for building and operating all living things. The DNA instructions are divided into segments called genes. Each gene provides the information for making a protein that carries out a specific function in the cell. These genes are found in chromosomes inside the cell's nucleus. Chromosomes are what get copied and passed on from generation to generation.
The DNA molecule consists of two strands that form a double helix, a spiraling shape much like a twisted ladder. The DNA molecule has a sugar part, a phosphate part and four different chemical bases - adenine (A), thymine (T), cytosine (C) and guanine (G). The backbone is formed by a chain of alternating phosphates and sugars. The sugar molecule in the backbone provides an attachment site for one of the chemical bases. The four chemical bases are the DNA's alphabet for forming codes that instruct a cell to make different proteins. The differences in these combinations result in the differences among all living organisms. In this DNA alphabet two bases link together at a time. Adenine always combines with thymine and cytosine always combines with guanine.
3a. Know and explain science information specified for the grade level.
4b. Describe or explain observations carefully and report with pictures, sentences, and models.
Pre-lab discussion: Discuss with students what traits are and give some examples. Explain that DNA is the chemical that passes traits from parents to offspring. Inform the students that we have 6 feet of DNA in every human cell and over 100 trillion cells in our bodies. Show students a diagram of DNA and explain the chemistry of the nitrogen bases and their bonding. If you make a model of the DNA from licorice and marshmallows you can show them what they will be making.
Instructional procedure: The DNA extraction and the DNA model building can be done simultaneously. Start the extraction first and then when the mixture needs to sit the students can begin working on the model.
Rio Tinto Hands-on Science Curriculum Team