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As part of an independent research project, a student studied a genetic condition suffered by members of his family - HSC - SSCE Biology - Question 17 - 2009 - Paper 1
Question 17
As part of an independent research project, a student studied a genetic condition suffered by members of his family. The student wrote the following summary: - I am... show full transcript
Worked Solution & Example Answer:As part of an independent research project, a student studied a genetic condition suffered by members of his family - HSC - SSCE Biology - Question 17 - 2009 - Paper 1
Step 1
Construct a pedigree of this family.
Answer
To construct the pedigree, begin by identifying each family member as a symbol:
- Squares represent males, and circles represent females.
- The affected individuals should be filled in, while unaffected individuals remain unfilled.
Draw the following relationships based on the provided information:
- Individual A (the student) is a male (square) and affected (filled).
- Individual B (mother) is a female (circle) and unaffected (unfilled).
- Individual C (father) is a male (square) and affected (filled).
- Individual D (father's brother) is a male (square) and affected (filled).
- Individual E (father's sister) is a female (circle) and unaffected (unfilled).
- Individual F (father's mother) is a female (circle) and unaffected (unfilled).
- Individual G (father's father) is a male (square) and affected (filled).
Connect the individuals with lines to show relationships:
- Draw horizontal lines between the parents (Individual B and Individual C) and a vertical line leading to the son (Individual A).
- Show the connections to other family members appropriately to depict brothers and sisters.
Step 2
Why are diagrams, such as pedigrees, useful in analysing data?
Answer
Diagrams like pedigrees are useful in analysing data as they visually represent family relationships and genetic conditions across generations. This allows for easier identification of inheritance patterns and can help in predicting how traits may be passed on within a family.
Step 3
Assess the validity of the student’s conclusion, and provide support for your assessment.
Answer
The conclusion made by the student, that the condition must be sex-linked as only males have it, is not necessarily valid. While it is a common association for certain conditions to be sex-linked, the statement lacks supporting evidence.
- Condition in Males: The presence of the condition in the father and the father’s brother suggests a possible inheritance pattern, but it does not confirm that the trait is exclusively sex-linked.
- Female Members: The absence of the condition in female relatives (mother, sister, and grandmother) needs to be assessed further. Some conditions may be autosomal recessive, where both parents would need to be carriers to express the condition in males, implying that the lack of the condition in females does not exclude it from being potentially inherited by males.
- Research and Evidence: A comprehensive analysis including genetic testing and assessment of family history would provide stronger support for determining if the condition is indeed sex-linked or if other inheritance patterns are involved.