1. Learning About Pedigrees

2. 2. A chart used to follow
genetic traits in a family
2. Can be used to determine
who a trait is inherited from
2. Can be used to determine if
a trait is dominant,
1. Pedigree recessive, X linked or some
other mode of inheritance.

3. Example of a Pedigree!

4. 1. Constructing a Pedigree
2. Males
represented by
squares
2. Females are
represented by
circles
2. A marriage is a
line between 2
shapes
2. Offspring are
shown using a line
from a marriage

5. 2. Shaded shapes show
people that have a
trait
2. Unshaded shapes do
not show the trait
2. Sometimes a
heterozygous person
is half-shaded

6. Practice – Write the answers to these
questions on a piece of paper.
1. In this pedigree, which numbers
are females?
2. Which numbers are male?
3. How many brothers does # 11
have?
4. Who is # 9 married to?
5. How many children does couple
1 and 2 have?
6. Which are married?
7. Which show the trait for which
the pedigree was constructed?
8. Guess: do you think this trait is
inherited as a dominant allele or
a recessive allele? WHY?

7. Practice – Write the answers to these questions
on a piece of paper. Use the numbers to show
which people are the answers to each question
1. In this pedigree, which numbers
are females?
1,4,7,8,10,11,13,15,16,17,18,19
2. Which numbers are male?
2,3,5,6,9,12,14,20
3. How many brothers does # 11
have? 1 (#12)
4. Who is # 9 married to? 8
5. How many children does couple
1 and 2 have? 3
6. Which are married? # 4 and #6
7. Which show the trait for which
the pedigree was constructed?
2,6,9,11,16,20
8. Guess: do you think this trait is
inherited as a dominant allele or
a recessive allele? WHY?

8. Try using a pedigree to determine
genotypes…..
• If this pedigree follows a
trait that is coded for by a
recessive allele….
• What is the genotype of
parent 1? A = dominant allele
a= recessive allele
• Parent 2?
• The daughter?
• The son?

9. Try using a pedigree to determine
genotypes…..
• If this pedigree follows a
trait that is coded for by a
recessive allele….
• What is the genotype of
parent 1? Aa
A = dominant allele
• Parent 2? Aa a= recessive allele
• The daughter? aa
• The son? A__ (we can’t
know the second allele yet)

10. Figure out if the trait is
dominant or recessive……
• Do you think this pedigree
shows a dominant trait or a
recessive trait?
• Explain why and draw a
punnett square to support
your answer.

11. • In this pedigree, the trait must be dominant,
and the parents must both be heterozygous
A a
A AA Aa
a
Aa aa

12. Summarize……
• List several types of information
that pedigrees can be used for.
• Explain how a pedigree is
constructed
• Explain whether the pedigree here
shows a dominant trait or a
recessive trait and explain why you
think so using a punnett square.

13. Try making a pedigree!
• The gene which results in Achondroplasia is dominant. Use
the numbers to make a pedigree which follows the genotypes
of each person in this picture. You can use the numbers to
show who is who on the pedigree.
3
4
5 6
1 2

14. Albinism is inherited as a recessive allele. In the figure above, assuming
that persons from the general population are not heterozygous for
albinism (Aa), what are the genotypes of all persons whose genotypes
are known?

15. Case Study
• Learn about a disorder called Alcaptonuria (click here).
• Read the fact sheet and determine the following :
• What are the SYMPTOMS of alcaptonuria?
• What are the CAUSES of alcaptonuria?
• What test determines whether a patient has
alcaptonuria?
• What are some effective treatments for
alcaptonuria?

16. The Story
A new baby is born into the family!! Baby Jenna appears
health and strong, but nurses notice that her diaper has
turned a disturbing brown/black color.
After testing, the doctor diagnoses the child with
alcaptonuria.
The family now needs to know more about the disease, so you
are called in to help.
Your goals:
1. Determine who in the family has the disease
2. Design a pedigree to help the family see how the trait
has moved through the family.
3. Explain how the trait is inherited in a way that the family
understands.

17. Start your research
• 1. Test the urine of the family.
 Request urine samples of family members
 Add the test solution to the tube
 Record the results.
• 2. Design a pedigree and indicate who is
affected and who is not (hint: you may benefit from designing
the pedigree before the test and then shading in the affected family members
later. )
• 3. Fill in the genotypes of each of the family
members on the pedigree.

18. • The family: John and Lucy are the parents of
baby Jenna
• John has 1 sister named Suzanne
• John’s parents are Steven and Martha
• Lucy’s parents are David and Ann
• Lucy has a brother, Randy and a sister Lynne