Does Genetic Information Affect Your Family?

Project #1464 on iSENSEProject.org

This project can be done in conjunction with a unit in Genetics. Students will have already learned that genetic information is passed on to offspring equally from both parents. They will have a solid understanding of how to create Punnett squares to predict the theoretical probability of certain outcomes of dominant and recessive genetic crosses. 

In this program, students will look at the probability of inheritance of a sex-linked disorder, Fragile X syndrome. In this disease, females can have one normal X chromosome and one affected X chromosome (XX connotes female), but they will not have the disease because their one good X chromosome can compensate for the bad X. She will be a carrier. However, if a male (XY) gets the defective chromosome, he will have the disease, because he does not have another X to mask the damaged one.

Students will use red, white and blue chips to simulate the probability of inheriting the disease as follows:

1. In a bag, place one red and one white chip. This is the mother's bag. (She's a carrier.)

2. In another bag, place one blue chip and one white chip. This is the father's bag.

3. Without looking, draw one chip from each bag and record results as follows:

•             two white chips are normal females (WW)
•             one red and one white are carrier females (RW)
•             one white and one blue are normal males (WB)
•             one red and one blue are affected males (RB) - they have the disease

4. Repeat this 10 times and record data on a separate piece of paper after each draw.

When done in class, students can add data through the contributor key. For purposes of this activity, I have collected my own data, choosing the chips for 50 trials.

Guiding Questions:

How many trials resulted in females? How many were carriers?

How many males were affected with the disease?

What's the percent chance of having a Fragile X affected male? Is this always true? What would help you make a more informed decision?

If you were a female in the mother's family, would you agree to be tested for this genetic disorder? Why or why not?