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Cool Tool: Marshmallow Meiosis: Breeding Reebops
Type: Activity
Topic: Meiosis, Random Assortment, Variation, Inheritance, Genotype & Phenotype
Grade Level: Middle school, high school, late elementary (with modifications)
Contributor: Lisa D. Comiskey
School: Chinook Middle School, Highline School District, Seattle, WA
Purpose: To explain how meiosis is responsible for the tremendous variation within a species.
References: Adapted from an article by P. Soderberg in The Science Teacher, Nov. 1992, pp. 28-31.
Activity Sheet: See Appendix II of the Genetics Education Guide, Supplementary Classroom Activity Materials, for student laboratory report form, Figure 1, and Table I. Download guide in pdf.
Materials: Marshmallows (large white and small colored), push pins, toothpicks, small nails, pipe cleaners, thumbtacks, tagboard or construction paper (cut up to form parental chromosomes), envelopes, copies of lab report form and Table I for each student or group (Appendix II), copy of Figure 1 for teacher.
Summary: Students uncover the principles of genetic variation when they breed "Reebops," imaginary creatures made out of easy-to-find materialsómarshmallows, tacks, and pipecleaners. Reebops have seven pairs of chromosomes, each carrying the gene for a trait that affects their outward appearance (phenotype). To prepare for the lab, assemble mom and dad Reebops, who are heterozygous for all seven traits. Divide the class into pairs and have students simulate meiosis by drawing parental chromosomes randomly (see below for instructions). Next, students assemble the resulting Reebop offspring. The entire class compares their offspring and notes the huge phenotypic variation. Baby Reebops can be displayed by hanging them from the ceiling and used as a source of discussion for the remainder of the genetics unit. A lab report form (see Appendix II) is provided for working out the genotypes and phenotypes and answering related questions.
Methods:
Pre-lab
1. For each parent, cut up seven pairs of different length strips from construction paper or tagboard to represent parental chromosomes. (Figure 1, Appendix I). Each student group will need a set of each parentís chromosomes.
2. Put green lines on dadís chromosomes and pink lines on momís chromosomes. Alternatively, use different colors of paper for each parent.
3. Label the chromosomes with the allele of the gene they carry as shown in Figure 1.
4. Using the Reebop Decoder Key (Table I, Appendix I), assemble the parent Reebops so that they are fully heterozygous for all seven traits. Each Reebop has a large white marshmallow head and either two or three marshmallow body segments. Attach the head and body segments to each other using toothpicks. It is easier to contruct Reebops if the marshmallows are left out overnight to harden slightly. Display the parental Reebops so that the class can examine their phenotypes.
Lab
5. For each group, provide an envelope of mom and dadís chromosomes (14 chromosomes per parent) and materials to construct Reebops.
6. Ask students to organize the chromosomes according to size and color.
7. Have students randomly select one chromosome of each size from mom and dad and place them in a "baby pile." (Perhaps use a coin toss to determine selection of dominant or recessive trait.) Students should return the unchosen chromosomes to the envelope.
8. Have students assemble their baby according to the Reebop Decoder Key (Table I, Appendix II). Ask students to complete #1 on the Breeding Reebops Lab Report (Appendix II).
9. Complete the remaining questions on the lab report (the questions assigned will depend on the grade level).
Classroom Use: Although best suited for older grades, this activity might, with modifications, be used in late elementary.
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last updated 06/15/04