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4. Haemophilia is a recessive sex-linked genetic disorder - Edexcel - GCSE Biology - Question 4 - 2016 - Paper 1
Question 4
4. Haemophilia is a recessive sex-linked genetic disorder. The letter h is used for the recessive allele and H for the dominant allele. The diagram shows the inherit... show full transcript
Worked Solution & Example Answer:4. Haemophilia is a recessive sex-linked genetic disorder - Edexcel - GCSE Biology - Question 4 - 2016 - Paper 1
Step 1
Step 2
Calculate the probability of person F and person G having a child with haemophilia.
Answer
To determine the probability, we will set up a Punnett square.
Punnett Square:
| X^H | X^h |
---------------------------
X^H | X^H X^H | X^H X^h |
---------------------------
Y | X^H Y | X^h Y |
From the Punnett square, the possible genotypes are:
- (normal female)
- (carrier female)
- (normal male)
- (affected male with haemophilia)
Thus, the probability of having a child with haemophilia is derived from the genotype, which occurs in 1 out of 4 offspring or 25%. Hence, the probability is 25%.