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?

Autosomal dominant

Sex-linked dominant

Sex-limited recessive

Sex-linked recessive

Solution

Sex-linked recessive

Sex linked characteristic is determined by the genes located on the sex chromosome ie X or Y. Sex limited characteristic is the condition where expression of sex linked genes is limited to one sex.

In the given problem, neither man nor woman are deceased by the disease. Therefore, women must be the carrier of the disease causing gene. Also, none of the daughters are suffereing from the disease except the sons, ie, daughters are also carrier.

Suppose, XY = genotype of man

X^dX = genotype of woman (d refers to disease causing gene)

The probability for each combination is 25%. Therefore, among seven children, 2 are normal daughter, 3 diseased sons and 2 normal sons are possible.

Some More Questions From Principles of Inheritance and Variation Chapter

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Principles Of Inheritance And Variation

Some More Questions From Principles of Inheritance and Variation Chapter

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