Question

Inheritance of which of the following traits is shown in the cross given below?

Choose the correct option from the following:

• A. ( \text{Autosomal recessive trait} )
• B. ( \text{X-linked dominant trait} )
• C. ( \text{X-linked recessive trait} )
• D. ( \text{Autosomal dominant trait} ) \

Answer 1

The Correct Option is C

The cross involves a normal man (XY) and a carrier woman (X\textsuperscript{C}X). The notation X\textsuperscript{C}X indicates that the woman has one normal X chromosome and one X chromosome carrying the recessive allele for a genetic disorder (represented by C). The offspring show the following genotypes: XX\textsuperscript{C} (Carrier daughter)
XX (Normal daughter)
XY (Normal son)
X\textsuperscript{C}Y (Diseased son) The fact that the disease appears only in the son and is inherited from a carrier mother suggests that the trait is X-linked recessive. Let's analyze why other options are incorrect: Autosomal recessive: If it were autosomal recessive, both parents would need to carry at least one recessive allele to have an affected child. Here, the father is normal. X-linked dominant: If it were X-linked dominant, an affected father would pass the trait to all his daughters. Here, the father is normal, and the mother is a carrier, passing it to some but not all offspring. Also, if the mother had the dominant trait, at least one of the daughters would show the trait if the father was normal. Autosomal dominant: If it were autosomal dominant, at least one parent would have the disease. Here, both parents are phenotypically normal (the mother is a carrier). Therefore, the inheritance pattern shown is consistent with an X-linked recessive trait.