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Pedigree Charts. The family tree of genetics. Overview. What is a pedigree? Definition Uses Constructing a pedigree Symbols Connecting the symbols Interpreting a pedigree. What is a Pedigree?. A pedigree is a chart of the genetic history of family over several generations.

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Pedigree charts

Pedigree Charts

The family tree of genetics


Overview
Overview

  • What is a pedigree?

    • Definition

    • Uses

  • Constructing a pedigree

    • Symbols

    • Connecting the symbols

  • Interpreting a pedigree


What is a pedigree
What is a Pedigree?

  • A pedigree is a chart of the genetic history of family over several generations.

  • Scientists or a genetic counselor would find out about your family history and make a pedigree chart to analyze and provide advice.


Constructing a pedigree

Male

Female

Constructing a Pedigree

Each generation is shown on a different ROW

Married Couples are connected and children come off BELOW them

Plan out the pedigree so marriages of each sibling are not interfering with the flow of the chart


Connecting pedigree symbols
Connecting Pedigree Symbols

Examples of connected symbols:

  • Fraternal twins

  • Identical twins


Connecting pedigree symbols1
Connecting Pedigree Symbols

Examples of connected symbols:

  • Married Couple

  • Siblings


Example
Example

Use the pedigree to answer the following:

How many generations?

How many married couples?

How many sisters?

How many sets of brothers?


Symbols in a pedigree chart

Affected

Autosomal carrier

Deceased

Additional? See the chalkboard

Symbols in a Pedigree Chart


Interpreting a pedigree chart
Interpreting a Pedigree Chart

  • Determine if the pedigree chart shows an autosomal or X-linked disease.

    • If most of the males in the pedigree are affected the disorder is X-linked

    • If it is a 50/50 ratio between men and women the disorder is autosomal.


Example of pedigree charts
Example of Pedigree Charts

  • Is it Autosomal or X-linked?


Answer
Answer

  • Autosomal

Rationale: Because there are 3 females and 3 males affected


Interpreting a pedigree chart1
Interpreting a Pedigree Chart

  • Determine whether the disorder is dominant or recessive.

    • If the disorder is dominant, one of the parents must have the disorder.

    • If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.


Example of pedigree charts1
Example of Pedigree Charts

  • Dominant or Recessive?

Hint: Add genotypes above each individual to determine the answer


Answer1
Answer

  • Dominant

dd

dd

Dd

Dd

dd

dd

dd

Dd

Dd

Dd

dd

dd

Dd


Example of pedigree charts2
Example of Pedigree Charts

  • Dominant or Recessive?


Answer2
Answer

  • Recessive

Dd

Dd

Dd

Dd

Dd / DD

Dd / DD

Dd

dd

dd

dd

Dd

Dd

dd


Summary
Summary

  • Pedigrees are family trees that explain your genetic history.

  • Pedigrees are used to find out the probability of a child having a disorder in a particular family.

  • To begin to interpret a pedigree, determine if the disease or condition is autosomal or X-linked and dominant or recessive.