Finally, inherited disorders and pedigree charts tied everything together. I studied a chart where a recessive condition like cystic fibrosis appears. Using symbols—filled for affected, half-filled for carriers—I labeled each generation’s genotypes. Then I predicted the probability that the next child would inherit the disorder.
I practiced by drawing multiple generations: assigning genotypes, connecting parents to children, and calculating probabilities. That stepwise approach demystified how genetic counselors give risk assessments.
Sample SPM Question
“In a family pedigree, two unaffected parents have one child with albinism (a recessive trait). Assign possible genotypes to the parents and calculate the chance that their next child will be affected.”
My answer:
- Parents: both Aa (carriers)
- Probability next child aa = ¼ or 25 %.
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