Grades 3-5: The Living Environment: Heredity - Some likenesses between children and parents, such as eye color in human
beings, or fruit or flower color in plants, are inherited. Other likenesses, such as people's table manners or
carpentry skills, are learned.
For offspring to resemble their parents, there must be a reliable way to transfer information from one generation to the next.
Grades 6-8: The Living Environment: Heredity - In some kinds of organisms, all the genes come from a single parent, whereas in organisms that have sexes, typically half of the genes come from each parent.
Students create and decode a "DNA recipe" for man's best friend to observe how variations in DNA lead to the inheritance of different traits. Strips of paper (representing DNA) are randomly selected and used to assemble a DNA molecule. Students read the DNA recipe to create a drawing of their pet, and compare it with others in the class to note similarities and differences.
For 28 envelopes:
1. Make eight copies each of DNA Strips A, B, C, and D (above) on colored paper choosing one color for each type of DNA Strip. For example:
2. Cut out the DNA strips on each page (a paper-cutter works well)
3. Place two DNA strips of each color in an envelope. The envelope should contain eight DNA strips total (four different colors).
4. Repeat step three until you have assembled 28 "Dog DNA" envelopes. Note: This is the minimum number of DNA strips per envelope that you need to carry out the activity. Adding
more DNA strips of each color increases the variety of possibilities for each trait.
1. Display different types of instructions (e.g. a recipe book, a blueprint, a DNA molecule) and ask students for what they might use these instructions. Explain that just as a recipe is used to cook a meal or a blueprint is used to build a home, DNA contains instructions that specify an organism's traits.
2. Read the beginning paragraph of A Recipe for Traits (instructions file, above) as a class.
3. Review the instructions (above). You may want to demonstrate how to use the Dog Traits Key (above) to read the DNA recipe and identify the first trait.
4. Remind students to leave the DNA strips they choose out of the envelope and tape them together in order. The resulting long strand will be their DNA recipe.
5. Have students work individually or in pairs to complete the activity. When students have finished, have them post their dog drawings on the wall along with the DNA recipe for their dog.
Are any two dogs alike? Point out that every dog shares some traits in common with others, but each has an overall combination of traits that is unique.
Variations in each DNA strand (the sequence of symbols) led to the inheritance of different traits.
The overarching goal of this activity is to introduce students to the simple idea that differences in DNA sequence (DNA recipe) = differences in traits (different looking dogs).
This activity is an imperfect model for introducing "genes" as a concept because:
1. Two copies of each gene are inherited, one from mom, the other from dad.
2. Most traits (such as body shape, or coat color) are determined by multiple genes, each with multiple versions (or alleles). [i.e. Coat color might be determined by the combined effect of 5 genes, not one as in this example]