Chance of having cystic fibrosis if only one parent is affected and other is normal –
**Core Concept**
Cystic fibrosis (CF) is an autosomal recessive genetic disorder caused by mutations in the CFTR gene. This means that a person needs to inherit two defective copies of the gene (one from each parent) to express the disease. The severity of CF can vary depending on the type and number of mutations.
**Why the Correct Answer is Right**
In an autosomal recessive pattern, if only one parent is affected (homozygous recessive) and the other is normal (homozygous dominant), the offspring can still inherit the defective gene from the affected parent. However, they won't express the disease because they only have one copy of the defective gene. This is known as being a carrier or heterozygous. The chance of inheriting two copies of the defective gene (one from each parent) is low, making the risk of having cystic fibrosis minimal.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
In autosomal recessive disorders like cystic fibrosis, carriers (heterozygous individuals) are generally asymptomatic but can pass the defective gene to their offspring. This is why genetic counseling is essential for families with a history of the disease.
**Correct Answer:** D.