A man and a women, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughter 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

The correct option is C Sex-linked recessive

gamete	22A+X	22A+Y
22A+X	22AA+XX - Normal	22AA+XY - Normal
22A+x	22AA+Xx - Carrier	22AA+xY - Diseased

A genetic characteristic that is determined by genes located on the sex chromosomes (X or Y) are called sex-linked characteristic and the condition where expression of sex-linked genes is limited to one sex is called sex-limited characteristics. In the given problem, the disease is the result of sex-linked recessive genes. As neither man nor woman shows signs of disease it means a woman would be a carrier for the disease-causing gene. In their children none of the daughters is suffering from disease, while the sons are suffering, it means daughters are also carrier (i.e., X-linked recessive). For instance, Genotype of male and female parents are 22AA+XY and 22AA+Xx (where X is dominant on x and x is disease causing in recessive combination). The results of the cross will be:

So, out of 4 children, 25% will be diseased. So, among seven children, 2 normal daughters, 3 diseased sons, and 2 normal sons are possible.

So, the correct answer is 'Option C- Sex-linked recessive'.