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Pedigrees

Pedigrees. A Pedigree allows you to trace an inherited (genetic) disease through a family. The pattern of a pedigree helps determine: If the disease is inherited If the disease is dominant or recessive Pedigrees use standardized symbols. Sickle Cell Disease Pedigree.

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Pedigrees

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  1. Pedigrees • A Pedigree allows you to trace an inherited (genetic) disease through a family. • The pattern of a pedigree helps determine: • If the disease is inherited • If the disease is dominant or recessive • Pedigrees use standardized symbols

  2. Sickle Cell Disease Pedigree

  3. Translating family information into pedigrees A girl with a genetic disease has 2 sisters and one brother. Her brother has the same disease, but her sisters do not. Her mother has the disease but her father does not. Draw pedigree here:

  4. Dominant or recessive? Copy these pedigrees into your notes • For each case, determine whether the disease is dominant or recessive • Assign genotypes for each individual Case #1 Case #2 Case #3

  5. “Guess and check”- Case #1 If the disease is DOMINANT: • All individuals without the disease must be homozygous recessive. • All individuals with the disease must have at least one dominant allele (they are either homozygous dominant, or they are heterozygous) aa aa aa aa A ? Is this possible? • NO, the person with the disease could not inherit a dominant “A” if both parents have only “aa” genotypes.

  6. “Guess and check”- Case #1 If the disease is RECESSIVE: • All individuals with the disease must be homozygous recessive. • All individuals without the disease must have at least one dominant allele (they are either homozygous dominant, or they are heterozygous) A? A? a a aa A? A? Is this possible? • YES, the person with the disease could inherit a recessive “a” if both parents are heterozygous “Aa” • Therefore, this pedigree shows a recessive disease.

  7. Case #2- Dominant or recessive? Try dominant disease alleles: Try recessive disease alleles: Is dominant possible? Is recessive possible?

  8. Case #3- Dominant or recessive? Try dominant disease alleles: Try recessive disease alleles: Is dominant possible? Is recessive possible?

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