Study the following carefully -(AI 05)Read the pedigree. Inheritance pattern of the disease in the family is –
**Core Concept**
The pedigree provided represents a pattern of inheritance where a specific trait or disease is passed down through generations, exhibiting a characteristic pattern of affected and unaffected individuals. This pattern is a classic example of X-linked recessive inheritance, where the disease-causing gene is located on the X chromosome and primarily affects males, who have only one X chromosome.
**Why the Correct Answer is Right**
In X-linked recessive inheritance, males are more frequently affected than females because they have only one X chromosome. If the disease-causing gene is present on the single X chromosome, males will express the disease, whereas females will be carriers if they inherit one normal and one affected X chromosome. The pedigree shows that the disease is more common in males and that females are typically carriers, indicating X-linked recessive inheritance.
**Why Each Wrong Option is Incorrect**
**Option A:** Autosomal recessive type - In autosomal recessive inheritance, both males and females are equally affected, and each parent is typically a carrier. The pedigree does not show this pattern, as males are more frequently affected than females.
**Option B:** Autosomal dominant type - In autosomal dominant inheritance, a single copy of the disease-causing gene is sufficient to cause the disease, and each parent has a 50% chance of passing the disease to their offspring. The pedigree does not show this pattern, as the disease is more common in males and females are typically carriers.
**Option C:** X-Linked dominant type - In X-linked dominant inheritance, females are more frequently affected than males because they have two X chromosomes, and one affected X chromosome is sufficient to cause the disease. The pedigree does not show this pattern, as males are more frequently affected than females.
**Clinical Pearl / High-Yield Fact**
A key feature of X-linked recessive diseases is that they are more common in males, and females are typically carriers. This pattern is due to the fact that males have only one X chromosome, whereas females have two X chromosomes, which provides some protection against the disease.
**✓ Correct Answer: D. X-linked recessive type**