Asked in HEC Phase I 2017 2017Moderate

Two parents hemophilic and other carrier, chances among the male offspring to be hemophilic:

Correct answer: B. 50%

  • A. 25%
  • B. 50%
  • C. 75%
  • D. 100%

Explanation

Haemophilia is a sex-linked recessive disorder, usually an inherited bleeding disorder in which the blood does not clot properly. According to the question, among male offspring 50% are normal and 50% are hemophilic as inherits the haemophilia X chromosome from carrier mother.

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About X-linked Recessive Inheritance

X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.

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