Written by Kelly A. Hogan, University of North Carolina at Chapel Hill
The genetic code is often described as being analogous to the written language. I expand this analogy to help students understand the hierarchy that exists in genetics, since I find many students don’t understand the relationship between a gene and a chromosome. Imagine a set of books, perhaps the Harry Potter series. The entire series on the shelf is analogous to the genome. Each book can be thought of as a chromosome. Within each book are chapters, these can be thought of as genes. Lastly, the 26 letters of the alphabet are arranged to make the variation of words within the genes. The genetic code has 4 letters to make unique arrangements/sequences. What would be the consequence if a few sentences or a chapter or an entire book was lost from the series? Would the story still make sense? (This would be analogous to mutations and chromosomal abnormalities.)
Written by Sheri L. Kuslak, University of North Carolina at Chapel Hill
– To practice using Punnett Squares to assess risks of inheriting a genetic disorder
– To illustrate the different use of the terminology when discussing genetic disorders including: genotype, carrier, homozygous, heterozygous, affected, unaffected, dominant, recessive
– To make genetic testing feel more personal to elicit discussion of some of the social and ethical impacts of genetic testing
Activity Description: Students will be assigned to a “family” in which several of their classmates become their siblings and their parents are one of four celebrity couples. They are given the genotypes of their parents for three fictitious genetic disorders: Spontaneous Death at 40 (SD40), Hot Pink Hair at 50 (HPH50), or Exercise Addiction (EA). As a group, the siblings must determine their risks of developing the genetic disorders and which disorders they would and would not be tested for. Students will then draw each Punnett Square on the board and discuss the pros and cons for testing for these traits.
Time Needed: Minimum of 40 minutes
Materials Needed: Worksheets including the table below and the Celebrity Parents for each group
- Break students up into groups of up to 7 students, assign and distribute one celebrity couple to each group.
- Ask students to work together to determine the percent risk of them developing each of the genetic disorders based on their celebrity parents’ genotypes, and discuss whether as a family they should get tested. (Estimated Time: 10-20 minutes.)
- Start with the SD40 gene and have a representative from each family come to the board and draw their familyPunnett Squarefor this gene. Have the students report the percent of offspring that would be affected by the disorder. Repeat with the HPH50 and EA gene.
Possible discussion questions:
- Would you get tested for SD40 if you knew there was a chance you were genotype dd? Is the test useful if there is no treatment? How is this phenotype similar to Huntington’s disease? (Huntington’s is dominant, so it is inherited differently, but the phenotype is similar.)
- If you decided to get tested and your genotype was dd, would you date? Would you have children?
- Would you get tested for HPH50? Why or why not?
- If your parents are still under the age of 50 and were never tested for HPH50 disorder, and you discover that you carry the mutant allele, what does that mean to one of your parents? What if instead of pink hair, it was that you tested positive for the dominant allele for Huntington’s Disease? What if your parent didn’t want to know their status, but you tested positive?
- If you inherit two copies of the e allele, will you develop Exercise Addiction? What precautions might you take if any if you knew this was your genotype?
- What if instead of being addicted to exercise you had an increased risk of alcoholism. Would you get tested for this? Would this affect how you approach drinking?
- A mutation in a gene for breast cancer (BRCA-1 or BRCA-2) can increase a woman’s risk for developing breast cancer as much as 50-80%. If you were at an increased risk of developing cancer of a specific organ, would you want to get tested? Would you take any preventative action?