Real-Life Math -- Solution
1. Depending on the combination of the sperm and egg, there are 4 possibilities for each pregnancy:
- child has 2 normal CF genes
- child has a normal CF gene from mother and mutated gene from father
- child has a mutated CF gene from mother and a normal gene from father
- child has 2 mutated CF genes (affected with CF disease)
Therefore, the probability of having a child with the disease is 1 in 4, or 25 percent, for each pregnancy. This risk is true only for couples who are both known to have 1 normal and 1 mutated CF gene.
2. Probability all 3 will have disease: 0.25 x 0.25 x 0.25 = 0.016
The probability that all 3 would have the disease is 1.6 percent.
3. There is a 25 percent chance the 2nd child would have CF. Previous pregnancies don't affect the probability.
Genetic counselors use math to calculate chances of inheriting a disease. Having strong math skills is a plus.
"They're important to a certain extent," says genetic counselor Elizabeth Hoodfar. "It depends on what particular subspecialty of genetic counseling you end up doing, but we do a lot of risk calculations, which is math."
Some genetic counselors work closely with laboratories that perform genetic testing and research. They, in particular, use math in the job.
"Some of the laboratory work involves some calculations, so that's where math skills come in," says Hoodfar.