Which human pedigree shows inheritance of a recessive, sex-linked characteristic?
A - HSC - SSCE Biology - Question 18 - 2021 - Paper 1
Question 18
Which human pedigree shows inheritance of a recessive, sex-linked characteristic?
A.
B.
C.
D.
KEY
○ Unaffected female
◻ Unaffected male
● Affected fema... show full transcript
Worked Solution & Example Answer:Which human pedigree shows inheritance of a recessive, sex-linked characteristic?
A - HSC - SSCE Biology - Question 18 - 2021 - Paper 1
Step 1
Identify the characteristics of sex-linked recessive inheritance
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Answer
In recessive sex-linked inheritance, the trait is typically expressed in males, as they have only one X chromosome. Affected males pass the trait to all daughters but none of their sons. Daughters who inherit the X chromosome carrying the allele may express the trait if they are homozygous for it.
Step 2
Analyze option A
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Answer
Option A shows affected males passing the trait to both sons and daughters, which is inconsistent with sex-linked recessive inheritance.
Step 3
Analyze option B
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Answer
In option B, affected daughters appear but no affected males are seen. This does not properly represent sex-linked recessive inheritance.
Step 4
Analyze option C
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Answer
Option C indicates that the affected male can pass the trait, but again does not meet the characteristic features needed for sex-linked inheritance.
Step 5
Analyze option D
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Answer
In option D, the affected male passes the trait to his daughters, who are affected but not sons. This pattern demonstrates recessive, sex-linked inheritance.
Step 6
Conclusion
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Answer
Based on the analysis, the correct pedigree that shows inheritance of a recessive, sex-linked characteristic is option D.
