Photo AI
Haemophilia is a recessive sex-linked genetic disorder - Edexcel - GCSE Biology - Question 4 - 2016 - Paper 1
Question 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 inheritanc... show full transcript
Worked Solution & Example Answer: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. Use the Punnett square for your answer.
Answer
To calculate the probability, we first identify the genotypes:
- Person F: X^H Y (affected male)
- Person G: X^H X^h (heterozygous female)
Constructing the 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, we can see the possible genotypes of the offspring:
- X^H X^H (not haemophilic)
- X^H X^h (carrier, not haemophilic)
- X^H Y (not haemophilic)
- X^h Y (haemophilic)
Thus, the probability of having a child with haemophilia is 1 out of 4, or 25%.