A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance do you suggest for this disease ?

Given that the disease affects only the sons and not the daughters, and both parents are unaffected, this pattern suggests an X-linked recessive mode of inheritance. In X-linked recessive diseases, males are more frequently affected than females because they have only one X chromosome. Females, on the other hand, would need to inherit two copies of the mutated gene (one from each parent) to express the disease, making it less common in females. The fact that the daughters are not affected but the sons are suggests that the mothers are carriers of the disease gene, and they have a 50% chance of passing the mutated gene to each son, who would express the disease, and a 50% chance of passing the normal gene to each son. Daughters have a 50% chance of inheriting the mutated gene from their mother, making them carriers like their mother, but they would not express the disease themselves unless their father also had the disease, which is not indicated. Therefore, the correct answer is option (D) Sex-linked recessive. Think of it this way: the disease's pattern of affecting only males and being transmitted by unaffected females suggests an X-linked recessive inheritance pattern.