Download Name - Humble ISD

Name: ____________________________
Date: ______________
Per. _________
Pedigree & Human Genetic Practice Worksheet
1. The following pedigree illustrates the inheritance of a recessive trait. Identify the genotypes of each
individual shown in the pedigree.
Key: _________________________________________________________
2. The following pedigree illustrates the inheritance of a dominant trait. Identify the genotypes of each
individual shown in the pedigree.
Key: _________________________________________________________
3. Examine the pedigree below showing the inheritance of albinism. Identify the genotypes of all individuals
a. Key: __________________________________________________
b. If individual E marries a man with albinism, what is the probability they would have a child with
the disorder? Cross: ____________________________
c.
If this same couple (E x albino male) has a child with normal pigmentation, what is the probability
their child is a carrier for albinism? ___________________________
4. Two couples, the Pages and the Bakers, had baby boys in the same hospital at the same time. There was
mix up in the nursery. Do Punnett squares to determine the biological parents of the babies. Us the
information given below to help you.
Name:
Mrs. Page
Blood Type:
B
Mr. Page
AB
Mrs. Baker
B
Baby #1 Belongs to the _____________________
Mr. Baker
A
Baby #1
A
Baby #2
O
Baby #2 Belongs to the ___________________
Sex-Linked
5. A hemophiliac man marries a woman who is a carrier of the hemophiliac condition. Draw a Punnett
square representing the offspring of this marriage.
a. What percentage of the offspring will be a hemophiliac? ___________
b. Is it possible for these parents to produce an offspring that is neither a
carrier nor a hemophiliac? ______________
c. If so, would this individual be male of female? ___________
d. What would be the genotype of this individual? __________
e. Is it possible to have a female hemophiliac? _____________
6. In the case of the sex-linked gene responsible for hemophilia, a hemophiliac father never transmits
hemophilia to his son. Explain why: ________________________________________________________
_____________________________________________________________________________________
7. Red-green color blindness is also a sex-linked recessive trait in humans. Using B as the superscript for
normal vision and b for color blindness, give the genotypes for the following:
a. A normal female:____________________
d. A normal male: _____________________
b. A carrier female: ____________________
e. A color blind male: __________________
c. A color blind female: _________________
8. In the following problems, draw Punnett squares to represent the crosses. Give the proportion (1/4, 2/4
ect.) of each phenotype listed. Note….. some phenotypes may not appear so you may leave those blank.
a. A color blind male x a female carrier
Normal female (not carrier) _______________
Color blind female
_______________
Carrier
_______________
Normal male
_______________
Color blind male
_______________
b. Normal vision male x color blind female:
Normal female (not carrier) _______________
Color blind female
_______________
Carrier
_______________
Normal male
_______________
Color blind male
_______________
c. Color blind male x normal female (not a carrier):
Normal female (not carrier) _______________
Color blind female
_______________
Carrier
_______________
Normal male
_______________
Color blind male
_______________
9. Can a normal blood clotting man & a carrier female have a hemophilic son? ________________
10. Why? __________________________________________________________________________
Complete the following autosomal crosses:
11. Is Huntington’s dominant or recessive? ___________________
12. What is the probability of a male heterozygous for Huntington’s and a homozygous recessive female
having a child with Huntington’s?
a. Phenotypic ratio: ______________________
b. Genotypic ratio: _______________________
13. The following pedigree shows the path of inheritance of hemophilia through several generations.
Identify the genotypes of each individual.
a. Key: ___________________________________________________________
Identify the genotypes of all the individuals in the pedigree.
If individual III-2 marries an unaffected woman whose dad had hemophilia, what is the probability that their son will be
hemophilic? _______________ What about their daughter? _______________ Show your work using a Punnett square!
If individual III-3 marries a non-hemophilic male, what is the probability that they will have hemophilic daughters? _____ sons? _____
Show your work using a Punnett square!
14. Fragile-X syndrome is a recessive sex-linked disorder located on the X chromosome. Below is a pedigree
tracing the passing of the fragile-X syndrome gene through 3 generations. Write in the genotypes on the
line next to /blow each individual.
15. Below is a recessive sex-linked pedigree tracing the red-green colorblindness gene located on the X
chromosome. Write in the genotypes on the line next to/below each individual.
16. A person with type A blood (unknown genotype) marries a person with type O blood. What
blood types are possible among their children. (Show 2 crosses)
_____________________________
17. Two people with type O blood have three children. How many of those three children also have
type O blood? _____________________________
18. Write
in the genotypes on the line next to/below each individual.
Tracing the path of an
autosomal dominant trait
Trait: Neurofibromatosis
Forms of the trait:
 The dominant form is neurofibromatosis, caused by the production of an abnormal form of the protein
neurofibromin. Affected individuals show spots of abnormal skin pigmentation and non-cancerous tumors
that can interfere with the nervous system and cause blindness. Some tumors can convert to a cancerous
form.
 The recessive form is a normal protein - in other words, no neurofibromatosis.
A typical pedigree for a family that carries neurofibromatosis is shown below. Use the letter "N" to indicate
the dominant neurofibromatosis allele, and the letter "n" for the normal allele.