Name: ________________________________________________________ Date: _________ Per: ___________
Pedigree Analysis
Pedigrees show INHERITED traits: traits that can be passed on from generation to generation. For
instance, a pedigree would never be used to illustrate which members of a family have a cold or the
chicken pox because this is not an inherited trait.
Match the following terms with the appropriate symbol:
Affected with trait,
mating,
male,
deceased (dead),
siblings,
female,
carrier for trait.
Symbols:
1. How many generations are in this
pedigree? __________
2. How many males are in this family?
II
____________
3. How many females are in this pedigree?
_________
4. Which individuals are carriers of the
trait? ____________
5. Which of the following traits would not
be shown in this pedigree?
a. Influenza (flu)
b. Dwarfism
c. Sickle cell disease
6. Explain your answer to #5. _______________________________________________________________________
_______________________________________________________________________________________________________
7. Some traits are lethal, which means they kill an individual. Is this trait lethal or non-lethal?
_________________________Explain your choice. ______________________________________________________
_______________________________________________________________________________________________________
8. What is the relationship between individual I-1 and II-2. (ex: mother-daughter? Grandmagranddaughter?) _________________________________________
9. What is the relationship between individual I-2 and III-12? _________________________________
HINTS:
If the trait is RECESSIVE, two copies of the allele must be present for it to be expressed. Only an
individual with a genotype like rr would have the trait. Individuals that are RR or Rr would not have the
trait.
 Parents are generally unaffected.
 Approximately 25% of children are affected if both parents are carriers.
 Two affected parents will always have an affected child. Recessive traits
often result from consanguineous
How do you recognize it?
Ask yourself:
Is there a situation in which the kids have the trait but the
parents do not?
If YES  Recessive
If the trait is DOMINANT, only one copy has to be present for it to be expressed. An individual with a GG
and a Gg, for instance, would both have the trait. An individual that is gg would not have the trait.
 Trait occurs every generation.
 When one parent is affected, approximately 50% of children will be affected.
 Affected individuals are usually heterozygous.
 Unaffected parents do not produce affected children.
 Two affected parents can have unaffected children.
How do you recognize it?
Ask yourself:
Is there a situation in which both parents DO have the trait,
but the kids DON’T?
If YES dominant
If the trait is SEX-LINKED Affected males always pass the condition to daughters and affected females are
homozygous recessive
 Children of an affected male (father) will not be affected. However, 100% of the female offspring
will be carriers of the disease.
 An unaffected carrier female (heterozygous mother) will have approximately 50% affected male
offspring and no affected female offspring (although approximately 50% of the female offspring
will be carriers).
How do you recognize it?
Ask yourself:
Is there a situation in which a MOTHER with the trait has
only SONS with the trait? Is there a situation where an
affected dad produces all carrier girls?
If YES sex-linked
Now, let’s try this out together:
1. How many generations are shown in this pedigree?
_______________
2. How many females are in this pedigree?______
3. Number the individuals.
4. List the individuals that DO NOT have the trait.
______________________________
5. What type of inheritance does this trait have?
a. Sex-linked
b. Dominant
c. Recessive
6. Which individuals are carriers in this pedigree?
_________________________________________________________________________________________________________________________
Now on your own:
7. How many generations are shown in this
pedigree? _______________
8. How many males are in this
pedigree?__________
9. Number the individuals.
10. List the females that DO have the trait.
______________________________
11. What type of inheritance does this trait
have?
a. Sex-linked
b. Dominant
c. Recessive
12. Which individuals are carriers in this pedigree?
13. Shade in the individuals that are carriers.
_________________________________________________________________________________________________________________________
14. How many generations are shown in
this pedigree? _______________
15. How many females are in this
pedigree? _____________
16. What type of inheritance does this
trait have?
a. Sex-linked
b. Dominant
c. Recessive
17. Shade in carriers in this pedigree?
18. Write in the genotype of as many
individuals that you can. If you cannot determine both alleles, just leave it as a blank (ex: E__)
Homework: Create a pedigree for Part A and fill in the chart for Part B using the “HINT” section of this
packet.
Part A: Pedigree
Brown eyes are a dominant eye-color allele and blue eyes are recessive. A brown-eyed woman whose
father had blue eyes and whose mother had brown eyes marries a brown-eyed man whose parents are
also brown-eyed. They have a son who is blue-eyed. Please draw a pedigree showing all four
grandparents, the two parents, and the son. Shade the whole individual if they express the trait and
shade half the individual if they carry the trait. Write in the genotype of as many individuals that you can.
If you cannot determine both alleles, just leave it as a blank (ex: B__)
Part B: Cheat sheet for pedigree analysis:
Type of
inheritance
Question to ask:
(Use review
sheet)
How can you
identify it?
(Draw a piece of a
pedigree)
Recessive
Dominant
Sex-linked