Introduction to Pedigrees
Name:
Biology 5.0
Date:
Period:
A pedigree is a chart that traces the pattern of inheritance of a particular trait within a family for several generations. By
analyzing a pedigree, scientists and genetic counselors can establish the nature of genes and alleles. They can tell whether
the allele is dominant or recessive. They can tell whether the allele is found on an autosome or a sex chromosome.
1.
The symbol(s) that is used to represent a father is/are
A.
B.
C.
D.
2. The symbol(s) that is used to represent a mother is/are
A.
B.
C.
D.
3. The symbol of a father who has the trait is
A.
B.
C.
D.
4. The symbol of a mother who has the trait is
A.
B.
C.
D.
5.
Show the union of the couple in the pedigree below:
6.
7.
8.
9.
10.
In the pedigree above, show that the man has a certain trait.
In the pedigree above, show that the couple has three children; the first two are daughters and the last is a son.
In the pedigree above, show that the middle daughter has the trait.
In the pedigree above, show that the first daughter married a man with the trait.
In the pedigree above, show that mom is a carrier (heterozygous).
Background Information. Pedigrees are used to trace a gene as it is passed from generation to generation.
The squares represent a male and the circles represent a female. In the examples in this handout, the shaded
circles and squares will represent having the disorder. Make sure to read each paragraph to find out if the
disorder is caused by dominant alleles or recessive alleles. A person can be a carrier of a trait, meaning they
have heterozygous alleles.
1. Cystic fibrosis is an autosomal recessive disease where mucus develops in the lungs, liver, and the
pancreas. Below is an autosomal pedigree tracing the passing of the cystic fibrosis gene through 3
generations. Write in the genotypes on the line next to/below each individual.
For all phenotype questions below, answers include: normal, carrier, has disorder.
2. What is the phenotype of individual 2? ________________________
3. What is the phenotype of individual 3? ________________________
4. What is the phenotype of individual 5? ________________________
5. What is the phenotype of individual 10? ________________________
6. What is the phenotype of individual 11? ________________________
7. Why did individual 9, 11, and 12 get the disorder but their parents did not have the disorder?
8. Albinism (Albino) causes deficiency of pigmentation in skin, hair, and eyes. Albinism is recessive and
autosomal. When a single gene affects many traits, like albinism, it is called pleitropy. Below is an
autosomal pedigree tracing the passing of the albinism gene through three generations. Write in the
genotypes on the line next to/below each individual.
9. Hemophilia is a recessive sex-linked disorder located on the X chromosome where a
person’s body can not control blood clotting or coagulation. Write in the genotypes on the
line next to/below each individual.
For all phenotype questions, answers include: male/female; and normal, carrier, has disorder.
10. What is the phenotype of individual 2? __________________________
11. What is the phenotype of individual 7? __________________________
12. What is the phenotype of individual 11? __________________________
13. Hemophilia is a recessive sex-linked disorder located on the X chromosome. Below is a sex-linked
pedigree tracing the passing of the hemophilia gene through 3 generations. Write in the genotypes on the
line next to/below each individual.
For all phenotype questions, answers include: male/female; and normal carrier, has disorder.
14. What is the phenotype of individual 1? __________________________
15. What is the phenotype of individual 4? __________________________
16. What is the phenotype of individual 6? __________________________
17. Below is a recessive sex-linked pedigree tracing the passing of the hemophilia gene located on the Xchromosome. Write the genotypes on the line next to/below each individual.
One of these genotypes is not possible. Which individual has a genotype that is not possible?
Why?