Name:___________________________
Date:______________
Period:_____
Complex Inheritance Study Guide
Directions: Show all the work and answers to each study guide question directly on this sheet. NOTE:
The textbook pages that correspond to this unit are PH text pp. 144-150.
_____ 1. Can you solve genetic problems involving the inheritance pattern called polygenic inheritance?
Work through problems #1-2 below and write your answers on this sheet. If you need help look
at the study hints at the end of this guide.
#1 A farmer notices that the length of his watermelons ranges from very long (dominant) to very short
(recessive) with many watermelons falling in-between at average lengths.
a. The trait of watermelon length is called polygenic inheritance? What does this term mean?
Write the definition.
b. Let’s say this trait is controlled by 4 different genes. Write the genotype (letter combinations)
of a very long watermelon.
c. Write the genotype (letter combinations) of a very short watermelon.
d. Write the genotype (letter combinations) of an average length watermelon.
#2. A person with black hair has the genotype AABBCC. A person with dirty blonde hair has the
genotype AAbbcc. If these two individuals mate. What will the genotype of their offspring be?
Remember, each parent can only contribute 1 allele (letter) per gene.
_____ 2. Can you solve simple genetic problems involving the inheritance of blood type (multiple alleles)?
Work through problem #1below and write you answers on this sheet. If you need help look at
the study hints at the end of this guide.
#1 If a type O person (recessive) marries a type AB person, what blood types could occur in their
children? Write the percent for each type.
%A ________
%B ________
%AB________
%O _________
Appendix_Science7
Name:___________________________
Date:______________
Period:_____
_____3. Can you solve more challenging genetic problems involving the inheritance of blood type (multiple
alleles)? Work through problems #1-3 below and write you answers on this sheet. If you need
help look at the study hints at the end of this guide.
#1 If a person heterozygous for type A blood marries a person homozygous for type B blood, what
blood types could occur in their children? Write the percent for each type.
%A ________
%B ________
%AB________
%O _________
#2 Jimmy has type A blood. Jimmy is about to undergo a routine operation, but the doctors still want
some blood on hand in case a transfusion is necessary. Jimmy’s mother has type A blood. Jimmy’s
father has type AB blood. His two cousins have type O and type B.
a. List the individuals that can give blood to Jimmy.
b. List the individuals can’t give blood to Jimmy.
#3 Two parents do not know their blood type. However, the couple has a 50% chance of having a child
with type B blood and a 50% chance of having a child with type O. Use a Punnett square to figure out
the genotypes of the parents.
Mom genotype - _____
Dad genotype - ______
Appendix_Science7
Name:___________________________
Date:______________
Period:_____
_____4. Can you solve simple genetic problems involving the inheritance of sex linked inheritance? Work
through problem #1 below and write you answers on this sheet. If you need help look at the
study hints at the end of this guide.
#1 Hemophilia (h) is a recessive disease caused by a gene found on the X chromosome. Therefore, it is
referred to as a sex – linked disease. The recessive allele (h) causes the disease. A normal man marries a
woman that is heterozygous for the trait. What is the chance that they will have a child with hemophilia?
Chance of child with hemophilia: ______%
_____ 5. Can you solve more complex genetic problems involving the inheritance of sex linked
inheritance? Work through problem #1 below and write your answers on this sheet. If you need
help look at the study hints at the end of this guide.
#1 Colorblindness (c) is a recessive, sex-linked trait. There is a 100% chance that two parents will have
a normal vision son and a 100% chance they will have a daughter who will carry the trait for
colorblindness (a sex-linked recessive trait). What are the genotypes of the parents?
Mom genotype - _____
Dad genotype - ______
_____6. Define the following genetic disorders,list the TREATMENTS, and say if it is recessive or
Sex-linked.
Cystic Fibrosis - ____________________________________________________
Sickle Cell Anemia - __________________________________________________
Hemophilia - ________________________________________________________
Tay Sachs - _________________________________________________________
Appendix_Science7
Name:___________________________
Date:______________
Period:_____
Study Hints:
Complex Inheritance Test
--------------------------------------------------------------POLYGENIC PROBLEMS
When a problem says “many different genes” it is polygenic. REMEMBER:
Upper case letters = Dominant
Lower case letters = Recessive
Look for the # of genes. For example: If height is controlled by 4 genes. . . A
person who is extremely tall would have the genotype AABBCCDD.
--------------------------------------------------------------------------------------------MULTIPLE ALLELES (BLOOD TYPE PROBLEMS)



When you are solving Blood Type problems REMEMBER multiple alleles (many ice cream
flavors, only 2 scoops!) and use I’s in the Punnett Squares:
IA IA , IB IB
 Heterozygous for Blood Type A or Blood Type B: IAi, IBi
 Blood Type O = ii
 Blood Type AB = IAIB

Homozygous for Blood Type A or Blood Type B:
--------------------------------------------------------------------------------------------SEX-LINKED PROBLEMS
When solving Sex-linked Problems REMEMBER to make an XX x XY Punnett Square
first:
 Females = XX
 Males = XY
 The gene is ALWAYS on the X chromosome. For eg: A woman with hemophilia (h)
is Xh Xh and a man with hemophilia is Xh Y (No gene on “Y”)
--------------------------------------------------------------MENDEL PROBLEMS
FLASHBACK! When solving problems that follow Mendel’s Pattern REMEMBER: You only
need to use uppercase (dominant) or Lowercase (recessive) letters.
T
t
TT
Tt
T
t
Tt
tt
Appendix_Science7