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Pedigree Charts
Background Information
Pedigree charts are very important to many different fields of science.
One reason they are important is because, they help scientists understand the
genetic patterns of diseases. It is important to be able to interpret pedigree
charts in order to learn the pattern of a disease or condition. Specifically,
using a pedigree chart, you can tell if the disease or condition is autosomal, Xlinked, dominant, or recessive.
Before you start this activity it is important to review these symbols:
Procedure:
A. First you need to become comfortable in making a pedigree chart.
Complete the following examples.
1. How can you tell if a couple is married on a pedigree?
Write a one sentence description and draw an example.
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2. How can you tell if the couple who is married had children? Write a one sentence description and draw an
example.
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3. Draw a pedigree that represents Mary married to Greg and with 2 sons (Scott and Tyler) and 1 daughter
(Karen). Please label the pedigree with the names of the people.
4. Draw a pedigree that represents Mary married to Greg, with 2 sons and 1 daughter. Their son, Scott,
married April and had Sutton (a boy) and Kendall (a girl). Their daughter, Karen, married Harry and had
Eliq (a son) and Tariq (a son). Please label the pedigree with the names of the people. Scott, Eliq and Tariq
are all color blind.
Created by Lauren Almaguer, CDC Science Ambassador, 2004.
The inheritance of genetic diseases
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 Sex linked disease are carried by sex chromosomes ( X or Y)
 In X-linked recessive, the disease only shows up in boys.
 The defective gene is on the X chromosome
 Women have two X chromosomes, so…at least one X will be normal which
mean women do not get the disease. They can, however, be carriers.
 Men only have one X chromosome (from their mother) (The Y comes from
their father). If the X chromosome is defective, they will have the disease.
 Mothers pass this disease to their sons. Fathers cannot pass on this disease.
 Examples: hemophilia, colorblindness, Duchene Muscular dystrophy
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Autosomal chromosomes = non sex chromosomes (pairs 1-22)
Because the disease is dominant, a single defective gene can cause the
disease
One of the parents will usually have the disease (since it is dominant.)
Only one parent must have the disease in order for the child to inherit the
disease.
Not all children will inherit the disease because even the parent with the
disease will usually have a healthy recessive gene that may be passed on.
Huntington’s Disease, Marfan’s Syndrome, Breast and ovarian cancer
Autosomal = non sex chromosmome
People with only one abnormal gene are called carriers, but since the gene is
recessive they do not exhibit the disease.
Both parents must be carriers in order for child to get the disease.
Examples: sickle-cell anemia, Tay-Sachs disease, cystic fibrosis
A. Identify the following pedigree charts as autosomal, X-linked, recessive, and dominant. Please explain
your answer.
1.
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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Created by Lauren Almaguer, CDC Science Ambassador, 2004.
2.
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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3.
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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B. Now you must make a pedigree chart from the descriptions given. Tell whether it is autosomal or Xlinked and whether it is dominant or recessive. Label the pedigree with the names of the individuals.
4.
Chad and Veronica got married and had Brittany, Kristin, and Harry. It was discovered that Harry had
muscular dystrophy. Brittany married Larry and had Steven and Stephanie. Steven also had muscular
dystrophy. Larry’s brother Barry also had muscular dystrophy but neither of their parents had the
disorder.
Is this disease Autosomal or X-linked? Explain
Draw a pedigree:
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Dominant or recessive? Explain.
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Created by Lauren Almaguer, CDC Science Ambassador, 2004.
5.
Lisa and Ashton got married and had three girls, Cari, Mary, and Sheri. It was discovered that Lisa had
muscular dystrophy. Sheri married Perry and had two boys, Pike and Tike. It was discovered that Sheri
and Pike had muscular dystrophy.
Draw a pedigree:
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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6.
Debbie married David and had three children, Darren, Dawn, and Derek. David, Darren and Derek
discovered they have muscular dystrophy. Derek married Didi and had two children, Denise and
Destiny. Denise also has muscular dystrophy and married Dirk. They had two children, Dee and
Devon. Dee has muscular dystrophy.
Draw a pedigree:
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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Extra Credit: Draw a pedigree of your family to show at least one inherited characteristic (hair color,
colorblindness, disease, etc.) Then determine if it is autosomal or x-linked, dominant or recessive.
Is this disease Autosomal or X-linked? Explain
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Dominant or recessive? Explain.
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Created by Lauren Almaguer, CDC Science Ambassador, 2004.