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1. Haemophilia is a recessive sex-linked disorder - Edexcel - GCSE Biology - Question 1 - 2014 - Paper 1
Question 1
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) ... show full transcript
Worked Solution & Example Answer:1. 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
Male offspring from A and B do not have haemophilia because:
- The condition is recessive and located on the X chromosome. Males inherit only one X chromosome from their mother and a Y chromosome from their father.
- Since B is a carrier, she has one allele for haemophilia (the recessive allele) and one normal allele. This means that there is a chance that male offspring inherit the normal allele from B, which would prevent them from having haemophilia. Furthermore, individual A does not have the allele for haemophilia, which means that the male offspring would not inherit the disorder.