AQA GCSE · Question 01.2 · Inheritance Variation and Evolution
Figure 1 shows the inheritance of MSUD in one family. The symbol for a male with MSUD is not in the key. What would this symbol represent?
How to approach this question
Look at the key provided with the diagram. A square represents a male, and a circle represents a female. Shaded (filled) shapes represent individuals with the condition (MSUD), while unshaded (empty) shapes represent individuals without it. The question asks what a shaded square would represent.
Full Answer
Male with MSUD
In pedigree charts, squares represent males and circles represent females. Shading is used to indicate individuals affected by a specific trait or condition. The key shows that a filled circle is a 'Female with MSUD' and an empty square is a 'Male without MSUD'. Therefore, a filled square must represent a male with MSUD.
Common mistakes
✗ Just writing "Male" or "With MSUD". The answer needs both parts.
✗ Confusing the symbols for male and female.
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