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Haemophilia is a recessive sex-linked disorder - Edexcel - GCSE Biology - Question 1 - 2014 - Paper 1
Question 1
Haemophilia is a recessive sex-linked disorder. This family pedigree shows the inheritance of haemophilia. (a) (i) State the sex chromosomes of person B. (ii) Exp... show full transcript
Worked Solution & Example Answer:Haemophilia is a recessive sex-linked disorder - Edexcel - GCSE Biology - Question 1 - 2014 - Paper 1
Step 1
Step 2
Explain why the male offspring from A and B do not have haemophilia.
Answer
The male offspring from A and B do not have haemophilia because:
- Male offspring inherit their X chromosome from their mother (B) and a Y chromosome from their father (A). Since B is a carrier but not affected, she can pass on an unaffected X chromosome.
- A is affected by haemophilia and contributes a Y chromosome. Therefore, the male offspring receive an unaffected X from B and a Y from A, resulting in them not having the disorder.