SME
Grade 9 Science · Problem type
A sex-linked pedigree
Use this for “Can an affected son have a mother who does not show the trait?”
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Three generations: a horizontal line joins partners, and a vertical line leads down to their children.
Two males show the trait: the grandfather and one grandson.
Assumptions
•
Squares are males and circles females; filled shows the trait, half-filled carries it.
•
Red–green color blindness is X-linked recessive: Xᵇ on the X chromosome.
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ABO blood types from genotypes
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DNA structure, replication and protein synthesis
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Use this for “A carrier mother and a father with normal vision: what is the chance a son is color-blind?”
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Use this for “Which two genotypes give the same blood type?”