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Mrs Stewart Honors Biology. Pedigree Charts. What is a pedigree?. Pedigree Charts. Record ancestry and/or trace the geneology of a trait through the family lines. Genetic Testing Medical History Historical Data Family Records. Why do we use them?

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Pedigree Charts

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Mrs Stewart

Honors Biology

Pedigree Charts

What is a pedigree?

Pedigree Charts

Record ancestry and/or trace the geneology of a trait through the family lines

  • Genetic Testing

  • Medical History

  • Historical Data

  • Family Records

Why do we use them?

Then what information do we use to determine inheritance of traits?


Pedigree Charts - Symbols

Pedigree Chart - Symbols


Example: Hemophilia in the royal family

How is Hemophilia inherited?

Sex-Linked Recessive Disorder

Example: Hemophilia in the royal family

What are some clues that you can see in this pedigree that could tell you this is a sex-linked disorder?


  • Albinism

  • Polydactyly

Pedigree Chart

How do we read a Pedigree?

  • Bill

  • Sam

Pam is Ann’s Grandmother

Which family members are Albino?

How is Ann related to Pam?

What are Inheritance Patterns?

Inheritance Pattern: The transmission of genetically encoded traits/conditions/diseases to offspring

In other words: How the gene is transmitted/passed on.

What are the different ways a genetic condition can be inherited?

Autosomal Recessive

Skips generations

Affects males/females equally

Pedigree may show carriers

Autosomal Dominant

There will not be carriers – those with the gene will be “affected”

Will probably not skip generations

Will affect males/females equally

Sex-Linked Recessive

More males affected than females

Skips generations

What is the inheritance pattern for this disorder?

Autosomal Recessive

  • How do we know?

    • “affected” skips generations

    • carriers

Enrichment Assignment

  • Create a family pedigree for the following trait:

    • Ability to taste “bitter”

  • Mrs. Stewart has strips of paper called PTC paper that will determine this ability.


The ability to taste PTC (bitter) is inherited.

BB = strong bitter taster

Bb = somewhat able to taste bitter

bb = cannot taste bitter

How to complete the enrichment assignment:

15 possible enrichment points

Have each family member (immediate household family) taste the PTC paper.

Use their responses to identify their genotypes

Create a pedigree that shows the trait throughout your family

10 points extra if you include pictures of each family member while tasting the PTC paper.

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