A man and a woman, who do not shwo any appaernt signs of a certian inherited disease, have seven chi

Question

A man and a woman, who do not shwo any appaernt signs of a certian inherited disease, have seven children (2 daughtters and 5 sons). Three of the sons suffre the siven disenase but none of the daughters are affected. which of the following mode of inheritanne do you suggest for this disease?

Accepted Answer

A gentic characteristic that is determined by genes located on the sex chomosomes (X or Y) are called sex linled characteristics and tha condition ehere expression of linked genes is limited to one sex is called sex limited characteristics. In given problem, disease is the result of sex-linked recessive genes. AS neither man nor woman show signs of disease it means womas would be carrier for disease causing gene. In their children none-daughterwere suffer from disease, while the sons were suffer, it means daughters are also carrier (ie, X-linkes recessive).
Suppose, genotype of man = X Y
Genotype of woman = Xd X
(d-disease causing gene)

For each delivery the probability for each combination is 25%. So, among seven children 2 normal daughter, 3 diseased sons and 2 normal sons are possible.

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