Case study·Hard exam skill (4/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
In a family, attached earlobe is recessive and free earlobe is dominant . Two parents with free earlobes have a child with attached earlobes.
Total: 4 marks
(a) What must be the genotype of the child? (1 mark)
(b) What can be inferred about the genotype of each parent? (2 marks)
(c) Explain why the parents show free earlobes. (1 mark)
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