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Recessive inheritance in pedigrees
AKU is a genetic disorder. Figure 3 shows the inheritance of AKU in one family.
Describe how Figure 3 shows that the allele for AKU is recessive.
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Marking points
- 1 Uses the pedigree to identify an affected child whose parents are unaffected/carriers.
Full-mark answer
A and B do not have AKU but their child D does, showing that two unaffected parents can carry and pass on a recessive allele.
Why this answer loses marks
The child has the AKU allele.
That does not show why the allele is recessive; the key evidence is an affected child born to parents who are both unaffected.