In a particular sex-linked disease, progressive weakening of the muscles and loss of coordination lead to death before the age of five - HSC - SSCE Biology - Question 15 - 2008 - Paper 1
Question 15
In a particular sex-linked disease, progressive weakening of the muscles and loss of coordination lead to death before the age of five.
Using this pedigree, what is... show full transcript
Worked Solution & Example Answer:In a particular sex-linked disease, progressive weakening of the muscles and loss of coordination lead to death before the age of five - HSC - SSCE Biology - Question 15 - 2008 - Paper 1
Step 1
Identify Individual 1's Genotype
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Answer
Individual 1 is a male and is unaffected. Therefore, he must have a normal genotype.
Thus, the genotype for Individual 1 is Normal.
Step 2
Identify Individual 2's Genotype
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Answer
Individual 2 is a female who is unaffected. Since she has an affected son (Individual 3), she must be a carrier for the gene.
Thus, the genotype for Individual 2 is Carrier.
Step 3
Identify Individual 3's Genotype
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Answer
Individual 3 is an affected male. In sex-linked diseases, males inherit the affected allele from their mother. Since Individual 2 is a Carrier, she passes the affected allele to Individual 3.
Thus, the genotype for Individual 3 is Affected.
Step 4
Conclusion
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Answer
Based on the above analysis, the genotypes of the individuals are as follows:
Individual 1: Normal
Individual 2: Carrier
Individual 3: Affected
Therefore, the correct answer is (C) Normal, Carrier, Affected.
