Let's say a couple, Priya and Rohan, are concerned about a genetic condition. Priya's brother has a condition called 'Cystic Fibrosis' (CF), which is recessive.

1. **Understand the inheritance:** CF is recessive, meaning you need two copies of the faulty gene (one from each parent) to have the condition. If you have one faulty gene and one normal gene, you are a 'carrier' but usually don't show symptoms.
---2. **Priya's status:** Since Priya's brother has CF, both her parents must be carriers. This means Priya has a 2/3 chance of being a carrier herself (she doesn't have the disease, so we exclude the possibility of her having two faulty genes).
---3. **Rohan's status:** Rohan has no family history of CF. The genetic counselor might suggest a simple blood test for Rohan to check if he is a CF carrier. Let's assume his test result comes back negative, meaning he is not a carrier.
---4. **Calculate the risk:** If Priya is a carrier (2/3 chance) and Rohan is not a carrier (0 chance of passing a faulty gene), then their child cannot inherit two faulty genes.
---5. **Counselor's advice:** The genetic counselor would explain that even if Priya is a carrier, since Rohan is not, their child will not develop Cystic Fibrosis. Their child could, at most, be a carrier like Priya.
---6. **Answer:** Priya and Rohan's child has a very low risk of developing Cystic Fibrosis because Rohan is not a carrier.