Donna moved among her students as they cut out the photocopied chromosomes from the handout. Unbeknownst to the students, there were 47 chromosomes, instead of the more typical 46 for humans, and when students made matched pairs, they would find an extra chromosome, do a little research in their packets, and recognize that the karyotype was indicative of a person with Down’s Syndrome. It was an activity that Donna’s cooperating teacher used every year during the genetics unit, and she was glad to see her high school students engaged in the lesson. She knelt down next to one group who was having a little trouble matching the chromosome pairs, and she drew their attention to the patterns of light and dark bands. “The size is more important than the shape,” she said, “and look at the alleles.” She pointed to the light and dark bands along the length of each chromosome shape on the photocopied handout. Of course, it was not scientifically accurate, but was an idea I had not heard before, and I was captivated. 1