Transcript We Are Family! Introduction to Pedigree Genetics

We Are Family!
Introduction to Pedigree Genetics
Mr. Nichols
PHHS
Cartoon of the Day: Get Punked!
Objectives
 The Student will be able to:
 1.) Finish the 2 trait Punnet square practice problems.
 2.) Sketch and describe the basic anatomy of a family
pedigree.
 3.) Use the information from a pedigree to infer genotypes
and answer application questions.
Are you ready for some Pedigrees?!?!
 Before we move on any questions regarding Punnett Squares?
What are Pedigrees?
 A pedigree is a diagram of family relationships that uses
symbols to represent people and lines to represent genetic
relationships.
 Pedigrees are often used to determine the mode of
inheritance (dominant, recessive, etc.) of genetic diseases.
 Autosomal: Refers to chromosomes that are NOT sex
chromosomes (xx or xy).
Anatomy of a Pedigree
Circle= Female
Square= Male
A line connecting a square
and a circle implies they
“mated.” Probably in the
early afternoon.
If a circle or square is
darkened, that means has a
particular trait or suffers
from a disease/disorder.
Different Modes of Inheritance:
1.) Autosomal Dominant
 Diseases or traits that exhibit an Autosomal Dominant
inheritance pattern follow the following rule:
A = the trait (a genetic disease or abnormality, dominant)
a = normal (recessive)
 Examples of autosomal dominant disorders:
Achondroplasia, pseudoachondroplasia, the multiple
epiphyseal dysplasias, chondrodysplasias, osteogenesis
imperfecta, Marfan syndrome, polydactyly, hereditary motor
sensory neuropathies I and II (Charcot-Marie-Tooth disease),
myotonic dystrophy, and neurofibromatosis.
Are these both examples of Autosomal
Dominant Pedigrees?
A
Explain your answer!
B
What are the genotypes
in pedigree B?
Quick Review Question! You know you love it!
 What can you conclude from these two examples about the
parents of a person that has a dominant characteristic?
 A.)If a person has a dominant trait, the parents will not have
the trait.
B.)If a person has a dominant trait, the parents might have
the trait or they might not have it.
C.) If a person has a dominant trait, at least one of the
parents will have the trait.
D.)If a person has a dominant trait, both of the parents will
have the trait.
Another Example: AwwYea!!
What are the
genotypes in this
pedigree?
Quick Review Questions: The Adventure
Continues!
 1.) Is it possible that this pedigree is for an autosomal
dominant trait?
 2.) Can two individuals that have an autosomal dominant
trait have unaffected children?
A.)If two individuals have a dominant trait, none of their
offspring will have the trait.
B.)If two individuals have a dominant trait, their offspring
might or might not have the trait.
C.)If two individuals have a dominant trait, their offspring
will have the trait.
We Are Family: Day 2
Introduction to Pedigree Genetics
Mr. Nichols
PHHS
Cartoon of the Day: Bear Season!
Different Modes of Inheritance:
2.) Autosomal Recessive
 Diseases or traits that follow Autosomal Recessive
inheritance patterns:
A = normal
a = the trait (a genetic disease or abnormality)
 Examples of Autosomal Recessive diseases: Cystic fibrosis,
sickle cell anemia (We will study this very soon), and Tay
Sachs disease.
Guess what: More Pedigrees!
 Assuming that the trait is recessive, write the genotype of
each individual next to the symbol.
Is this an example of an
Autosomal Recessive
Pedigree?
What About this one?
Assuming the disorder
is recessive, is this an
example of an
Autosomal Recessive
pedigree?
Write in the Genotypes
for each individual.
Quick Review Question: Great things
come in 3’s 
 1.) If a trait is autosomal recessive, what can you conclude
about the children if both parents are affected?
 A.) If both parents are affected, none of the children will be
affected.
B.)If both parents are affected, the children might or might
not be affected.
C.)If both parents are affected, all of the children will be
affected.
Hmm, what about this one?
Is it possible that this
pedigree is for an
autosomal recessive trait?
What are the Genotypes
for these individuals?
Quick Review Question: 
 If a trait is autosomal recessive, what can you conclude about
the children of two parents that are not affected?
 A.) If two parents have a dominant trait, the children will not
have the trait.
B.) If two parents have a dominant trait, the children might
or might not have the trait.
C.) If two parents have a dominant trait, the children will
have the trait.
Challenge Question 1
Assign Genotypes as usual.
Can this pedigree possible
represent an Autosomal
Recessive disease?
What does this pedigree
infer about recessive traits?
Different Modes of Inheritance:
3.) X-Linked Recessive
 The sex of an individual has been linked to certain disorders,
we’ll finish by examining these pedigrees.
 New Nomenclature
XA = normal Xa = the trait (a genetic disease or abnormality)
Y = Y chromosome (males only)
 Examples for a Female: XAXa, XAXA, XaXa
What would the male sex genotype look like?
 Examples for Males: XAY, XaY 
Let’s Practice
Assign the genotypes
(Use X and Y’s now).
Is it possible that the pedigree
above is for an X-linked
recessive trait?
Keep Going, almost there!
Assign the genotypes
(Use X and Y’s now).
Is it possible that these
pedigrees represent an X-linked
recessive trait?
Last Quick Review Questions!
 What can you conclude about the children of mothers affected
with an X-linked recessive trait: If the mother has an X-linked
recessive trait, the children will not have the trait.
A. )If the mother has an X-linked recessive trait, the children
might or might not have the trait.
B.) If the mother has an X-linked recessive trait, all of the children
will have the trait.
C.) If the mother has an X-linked recessive trait, females will have
the trait but males will only have the trait if their father also has the
trait.
D.) If the mother has an X-linked recessive trait, males will have
the trait, but females will only have the trait if their father also has
the trait.
Last Quick Review Questions! A New Hope!
 What can you conclude about the father of an affected
female?
 A.)The father of an affected female will not be affected.
B.) The father of an affected female might or might not be
affected.
C.)The father of an affected female will be affected.
Why is this so? Let’s Explore that tomorrow!
Different Modes of Inheritance:
4.) X-Linked Dominant
 XA =the trait (a genetic disease or abnormality)
Xa = Normal
Y = Y chromosome (males only)
 Common X-Linked Dominant Diseases: Few and Rare!
 Vitamin D resistant rickets
 Rett's syndrome
 Fragile X syndrome
Getting the hang of this yet? Let’s see!
Our First Genetic Case Study!
 When Queen Victoria of England was seventeen, she met one
of her many cousins, Prince Albert of Saxe-Coburg. She fell
deeply in love with him, and several years later, when they
were both twenty years old, Victoria proposed to Albert.
 They were married on February 11, 1840; both were
deliriously happy, and Victoria made Albert Prince Consort,
giving him an equal say in the running of the country. What
neither of them knew at the time was that Victoria was
carrying the gene for hemophilia.
Your Mission!
 You are a genetic detective tasked with figuring out what type of
inheritance pattern this disease is following in Queen Victoria’s
family pedigree.
 You’ve conducted your preliminary research and constructed a
rough pedigree of the family history. You’ve also concluded that
the disease is not autosomal.
Homework!
 Create a simple Pedigree of your own family!
 Figure out whether a trait (eye color, hair color, a disease) has
an autosomal dominant or autosomal recessive behavior.
 2 Generations are required
but 3 would be best.
 Pedigree Practice Problem Sheet (Both)
 All of this is due Friday!!!! 
Example