Fig. 3

Two paper-based activities in the Heredity module model the two sources of genetic variation. In “Mutate a DNA Sequence” (left), students introduce a random mutation into a gene and see its effect on the protein product. In “Build-a-Bird” (right), students use paper models of chromosomes to carry out the crossing-over step of meiosis. They randomly combine chromosomes from two parents and decode the alleles to draw a pigeon with the appropriate traits. As a class, they see how recombination and the random combining of parental chromosomes can generate offspring with a variety of trait combinations that were not present in the parents