Part of Lesson Plan: The Perfect Pair of Genes!

Activity Overview / Details

Materials Needed: Coat hangers (2), safety pins (20), jeans (2), T-shirts (2), shorts (2), gloves (2), socks (2)

Prior to class create a giant model of two homologous chromosomes using common clothing items. Each item of clothing represents a gene on the chromosome. String clothing together using safety pins and attach to a coat hanger at the top. Attach the coat hanger to the ceiling so that the chromosomes hang next to one another. One chromosome may begin with a pair of jeans, attached to a t-shirt, shorts, glove, and sock. The second chromosome, which is the homologous pair of the first, should have clothing assembled in the same order. However, some of the items may have variation. For example, begin building each chromosome with a pair of blue jeans. If the blue jeans are identical, the individual (whose chromosomes we are analyzing) is homozygous for that trait. Moving down the chromosome, if the t-shirts are two different colors, the individual is heterozygous for that trait. Continue in this fashion, including homozygous and heterozygous gene pairs. Refer to the supplemental handout "Building Your Chromosomes" for more information.



Walk students through this abstract example of a pair of chromosomes, making important curricular connections along the way. Begin by asking students to recall where DNA is located in a eukaryotic organism. (nucleus) How is DNA organized? (coiled into chromosomes) What are genes? (sections of DNA on a chromosome) What do genes code for? (traits) Refer back to the traits identified in the opening hook.



Describe each section of the chromosomes as you walk through the chromosome model. Help students identify homozygous and heterozygous traits. Share specific examples of traits each gene pair might code for to bring the illustration to life. Connect to previous knowledge by having students recall what homologous chromosomes are (chromosomes which are of similar size and shape that code for the same traits) and where these chromosomes came from (one from mom and one from dad).

Introduce the concept of dominant and recessive genes as you encounter a heterozygous pair. Briefly explain that genes interact in different ways. Sometimes one gene is expressed and the other is not. This gene is considered dominant, while the other is recessive. For example, if you have a blue sock and a white sock, explain that these might be genes coding for feather color in birds. If we assume the blue sock (gene) is dominant, what color will the bird be? (blue) Resist the urge to go too far into gene interaction at this point, to ensure that students get the basic concept of dominant and recessive traits. Further gene interaction can be explored at a later time. 



This activity was adapted from: Vogt, J, & Yale, M. From genes to jeans. Retrieved from http://www.cfaitc.org/LessonPlans/pdf/407.pdf