Cystic Fibrosis
Casey Kriak
Joe Scalora
Seyi Akinsola
January 27, 2010
Period 9-10
Summary of Cystic Fibrosis
• A genetic disorder that affects your respiratory and
digestive system
• Cystic fibrosis is a autosomal recessive trait; meaning it
requires to lower case letters
• You can be a carrier without having the disease; this
means that your kids can have it
• Symptoms: coughing or wheezing, respiratory sickness,
weight-loss, greasy stool, and salty tasting skin
• Cystic fibrosis causes 2 to 5 times more salt in your
sweat
• There is no known treatment, but there is medicine
that clears up the mucus from the lungs to prevent
lung infection; which can extend the life of a patient
What Chromosome is it on?
• Cystic Fibrosis is located on
the defected gene on
chromosome 7.
• CFTR (Cystic Fibrosis
Transmembrane conductance
Regulator
Mode of Inheritance
• Cystic Fibrosis is an autosomal recessive disease, meaning both
parents must pass on the defective gene to their child in order to
get the disorder. If the child inherits only one copy of the bad
gene, he/she is a carrier. Carriers don’t usually have the disease,
but they could pass it onto their kids.
What are Alleles?
• Alleles are traits that each gene carry represented with letters (eye,
hair color etc.)
• Half of the alleles come from your mother and half of the alleles
come from your father
• Each parent gives 2 alleles. The alleles are combined like a
multiplication table and the new-born baby’s odds are made.
• Alleles could either be dominant or recessive. Brown eyes and right
handed are examples of dominant and green eyes and left handed
are examples of recessive.
• The traits are resembled in letters. F-dominant f-recessive. Two of
the possible are combined in a punnet square. Ex. FF Ff, or ff. Any
time a dominant allele is matched with a recessive allele the
dominant wins
• Sex linkage uses X and Y’s. This determines what gender your child
will be. A female is a homozygous link(XX) and a male is a
heterozygous link (XY)
What is a Punnett Square?
• A Punnett square is a diagram that predicts to
offspring of two parents using alleles.
ANOTHER
PREDICTION
c
c
ANOTHER
PREDICTION
b
b
C
Cc
Cc
B
Bb
Bb
c
cc
cc
B
Bb
Bb
HOMOZYGOUS
DOMINANT
A
a
A
AA
Aa
a
Aa
aa
HETEROZYGOUS
DOMINANT
HOMOZYGOUS
RECESSIVE
PROBABILITY
• RATIOs: The Homozygous Dominant is (AA),
the heterozygous Dominant is (Aa), the
A
a
Homozygous Recessive is (aa).
A
AA
Aa
a
Aa
aa
- ¼ is (AA): ½ is (Aa): ¼ is (aa)
• PERCENTAGES: The Homozygous Dominant is
(AA), the heterozygous Dominant is (Aa), the
Homozygous Recessive is (aa).
- 25% is (AA), 50% is (Aa), 25% is (aa)
Phenotype/ Genotype
• What these letters Mean? BB? Bb? Bb?
• Let’s say A was brown eyes and a was blue eyes and A is the dominant trait
while a is recessive. (dominant trait shown on the organism.)
• Phenotype is what is shown on the organism.
- AA=brown eyes
A a
- Aa=brown eyes (with a blue eyes carrier)
- aa=blue eyes
A AA Aa
• Genotype is what is in the genes of the organism
a Aa aa
- AA= HOMOZYGOUS DOMINANT
- Aa= HETEROZYGOUS DOMINANT
- aa= HOMOZYGOUS RECESSIVE
Cystic Fibrosis is aa because it is a recessive trait.
Possibilities
A
a
A a
AA Aa
Aa aa
• Phenotype:
- Ratios: ¾ chances the child would have brown eyes, ¼ chances the
child would have blue eyes.
- percentages: 75% out of 100% the child would have brown eyes,
25% out of 100% the child would have blue eyes.
• Genotype:
- Ratios: ¼ is HOMOZYGOUS DOMINANT (AA) , ½ is
HETEROZYGOUS DOMINANT( Aa), and ¼ is HOMOZYGOUS
RECESSIVE (aa)
- Percentages: 25% is HOMOZYGOUS DOMINANT(AA) , 50% is
HETEROZYGOUS DOMINANT (Aa), 25% is HOMOZYGOUS
RECESSIVE (aa)
Student Practice
Autosomal Recessive Pedigree
Generation 1
1
Generation 2
Generation 3
1
1
-Male
-Female
2
1
2
1
2
2
2
No Fill- Carrier of Cystic Fibrosis
Filled- Has cystic Fibrosis
1
1
2
2
3
Now you try!
Generation 1
1
Generation 2
Generation 3
-Male
-Female
1
1
2
2
2
1
3
1
2
2
No Fill- Carrier of Cystic Fibrosis 1. If the parents have two kids, how
many will have cystic fibrosis?
Filled- Has cystic Fibrosis
2. The one kid with CF marries a
carrier how many of her 2 kids
have cystic fibrosis?
3. What do you think would happen if
the female on the right in G3
married a male with CF?