Principle of Inheritance and VariationEasyBloom L1
Question
Haemophilia is mentioned as a trait carried by the mother and passed to her sons. What is the pattern of inheritance for this trait?
Options
A.Haemophilia is an allele carried on one of the mother's autosomal chromosomes.
B.Haemophilia is an allele carried on the Y chromosome because more males have this genetic disorder than females.
C.Haemophilia is an allele carried on the X chromosome and can be directly inherited by the son from the father or the mother.
D.Haemophilia is carried on the X chromosome and can only be inherited by the son if the mother is a carrier.
Solution
Sol.(d) [Key Concept: Haemophilia — X-linked Recessive Inheritance Pattern] Haemophilia is carried on the X chromosome and can ONLY be inherited by the son from his MOTHER (from her X chromosome). A father gives his son the Y chromosome (not X), so sons cannot inherit X-linked traits directly from their father. A carrier mother (X^H X^h) passes either X^H or X^h to sons — sons receiving X^h will have haemophilia. This is the characteristic criss-cross inheritance of X-linked recessive traits.
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