In the pedigree shown, individuals that must be heterozygous for PKU include
A - VCE - SSCE Biology - Question 13 - 2008 - Paper 1
Question 13
In the pedigree shown, individuals that must be heterozygous for PKU include
A. 1–2
B. 1–4
C. II–1
D. II–6
Worked Solution & Example Answer:In the pedigree shown, individuals that must be heterozygous for PKU include
A - VCE - SSCE Biology - Question 13 - 2008 - Paper 1
Step 1
A. 1–2
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Answer
Individual 1–2 must be heterozygous for PKU if they have an affected child. In a pedigree where PKU is recessive, if an affected individual (with PKU) reproduces with an unaffected individual who has an affected child, the unaffected individual must be a carrier (heterozygous). Hence, individual 1–2 is heterozygous.
Step 2
B. 1–4
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Answer
Individual 1–4 may not be heterozygous since they are not represented as having any offspring affected by PKU. Without evidence of affected offspring, we cannot assume that they are heterozygous.
Step 3
C. II–1
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Individual II–1 could potentially be heterozygous if an affected child is shown in the pedigree. If they have an affected sibling, it’s likely they carry the gene, thus being heterozygous.
Step 4
D. II–6
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Answer
Similar to II–1, individual II–6 would also be heterozygous if there are affected individuals in their lineage. Their heterozygosity can be concluded if both parents are carriers.
