Name: _________________________
Pedigrees
A Sample Pedigree Chart or Family Tree
Key for Pedigrees
Study the pedigree for the dominant trait of unattached earlobes shown below. The darkened shapes
have the unattached earlobe trait.
1. In a pedigree, a square represents a male. If it is darkened he has unattached earlobes; if clear, he
has attached earlobes.
a. How many males represented in the pedigree have unattached earlobes? ______________
b. How many males have attached earlobes? ________________
2. A circle represents a female. If it is darkened, she has unattached earlobes; if clear, she has
attached earlobes.
a. How many females represented in the pedigree have unattached earlobes? ______________
b. How many females have attached earlobes? ________________
3. A marriage is indicated by a horizontal line connecting a circle to a square. How many marriages are
indicated in the pedigree? __________________
4. A line perpendicular to a marriage line indicates the offspring. If the line ends with either a circle or
a square, the couple had only one child. However, if the line is connected to another horizontal line,
then several children were produced, each indicated by a short vertical line connected to the
horizontal line. The first child appears to the left and the last on to the right. How many children did
the first couple have? ________________
5. The Roman numeral “I” represents the first generation. The Roman numeral “II” represents the
second generation, and so on. How many generations are represented in the pedigree?
________________
6. The genotypes of attached earlobes in the pedigree are easy to determine, since attached earlobes is a
recessive trait. Any clear circle or square will have the genotype of ee. Label the genotypes of all the
clear shapes on the pedigree as “ee”. How many people have the genotype ee? _________________
7. Individuals that show the trait for unattached earlobes are either Homozygous Dominant (EE) or
Heterozygous (Ee). Examination among the traits of the individual’s offspring and/or parents can
often determine the genotype. If the son, daughter, mother, or father has attached earlobes, ee, the
individual is heterozygous. Example: Individual II-4 has unattached earlobes. Because this
individuals mother (Individual I-2) has attached earlobes, we know that individual II-4 is
heterozygous, Ee. We can also look at individual II-4’s children. Because her sons and/or daughters
(Individuals III-6, III-8, III-9, or III-10) have attached earlobes, we know that individual II-4 is
heterozygous, Ee. Label the genotypes of all the darkened shapes on the pedigree that are
heterozygous, “Ee”. What is the genotype of the male in the first generation? ________________
8.
Individuals whose shapes are darkened have the trait for unattached earlobes and are either
homozygous dominant (EE) or heterozygous (Ee). If they have four or more children that all have
unattached earlobes, the individual is likely to have a homozygous Dominant (EE) genotype. If they
have fewer children the genotype is less certain. Label any individual that fit this criteria “EE”. How
many individuals in the pedigree have the genotype EE? ___________________
Study the pedigree for the Recessive trait of albinism shown below. The darkened shapes have the albino
trait.
9. If the shape is darkened he is albino; if clear, he has normal pigmentation.
a. How many males represented in the pedigree are albinos? ______________
b. How many males have normal pigmentation? ________________
10. If the shape is darkened she is albino; if clear, she has normal pigmentation.
a. How many females represented in the pedigree are albinos? ______________
b. How many females have normal pigmentation? ________________
11. How many marriages are indicated in the pedigree? __________________
12. How many children did the couple in the second generation have? ________________
13. How many generations are represented in the pedigree? ________________
14. The genotypes of albinism in the pedigree are easy to determine, since albinism is a recessive trait.
Any darkened circle or square will have the genotype of aa. Label the genotypes of all the darkened
shapes on the pedigree : ”aa”. How many people have the genotype aa? _________________
15. Individuals that show the trait for normal pigmentation are either Homozygous Dominant (AA) or
Heterozygous (Aa). Examination among the traits of the individual’s offspring and/or parents can
often determine the genotype. If the son, daughter, mother, or father is albino, aa, the individual is
heterozygous. Label the genotypes of all the clear shapes on the pedigree that are heterozygous
“Aa”. What is the genotype of the first male in the first generation? ________________
16. Individuals whose shapes are clear have the trait for normal pigmentation and are either homozygous
dominant (AA) or heterozygous (Aa). If they have four or more children that all have normal
pigmentation, the individual is likely to have a homozygous Dominant (AA) genotype. Label any
individual that fit this criteria with “AA”. If they have fewer children the genotype is less certain.
Label any individual that fits this criteria with a “A?”. How many individuals in the pedigree have
the genotype AA? ___________________