SME
Grade 7 Science · Problem type
Reading a pedigree
Use this for “Neither parent shows the trait but a child does. What are the parents’ genotypes?”
Explore
Three generations, numbered I, II and III.
Assumptions
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Squares are males, circles females. A filled symbol shows the trait.
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A line joins parents; their children hang below, oldest on the left.
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The trait comes from a recessive allele a: only aa shows it.
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The family took a genetic test, so the chart marks every carrier. From the chart alone, some unaffected people could be AA or Aa.
Topic check
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