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Duchenne muscular dystrophy is a sex-linked recessive genetic disorder caused by a mutation on a single gene on the X-chromosome - Edexcel - GCSE Biology - Question 5 - 2016 - Paper 1
Question 5
Duchenne muscular dystrophy is a sex-linked recessive genetic disorder caused by a mutation on a single gene on the X-chromosome. The letter D can be used for the d... show full transcript
Worked Solution & Example Answer:Duchenne muscular dystrophy is a sex-linked recessive genetic disorder caused by a mutation on a single gene on the X-chromosome - Edexcel - GCSE Biology - Question 5 - 2016 - Paper 1
Step 1
What is the percentage chance of any child from person A inheriting the mutated allele?
Answer
To determine the percentage chance of any child from person A inheriting the mutated allele, we first recognize that person A has a normal genotype represented as X^D X^B (assuming A is female and carries no mutated allele). Person A can only pass the X^B allele to her children. Therefore, the chance of any child inheriting the mutated allele (X^d) from person A is 0%. Thus, the answer is A: 0%.
Step 2
Explain the conclusion that can be made about the genotype of person C.
Answer
From the pedigree chart in Figure 5, since person C is connected to person A (who is normal and does not carry the mutated allele), we can conclude that person C must also have the normal genotype. Since both parents (person D and A) do not carry the mutated allele, this leads us to deduce that person C does not possess the mutated allele and must have the genotype X^D X^D.