 Cystic
Fibrosis is an inherited chronic disease
 It affects the lungs and digestive system
 Symptoms


It clogs the lungs with phlegm and causes lifethreatening infections
"obstructs the pancreas and stops natural enzymes from
helping the body break down and absorb food."
 Interesting

Facts
Cystic Fibrosis is nicknamed "65 Roses" because children
say it that way when they are diagnosed.
What Chromosome is Cystic Fibrosis Located On?
•People with cystic fibrosis inherit a
defective gene on chromosome 7 called
CFTR (cystic fibrosis transmembrane
conductance regulator).
•The protein produced by this gene
normally helps salt move in and out of
cells. If the protein doesn't work, the
movement is blocked and an
abnormally thick mucous is produced.
•The cells most seriously affected by
this are the lung cells. This mucous clogs
the airways, and increases the risk of
infection.
This condition is inherited in an autosomal recessive
pattern
 This means both copies of the gene in each cell have
mutations. The parents of an individual with an
autosomal recessive condition each carry one copy of
the mutated gene
 A person gets cystic fibrosis when he or she inherits
two mutated CFTR genes; one from each of their
parents. The parents don’t have it because they have
one dominant allele that isn’t mutated but the child
would have the two recessive


What Are Alleles?
Alleles are one member of a pair or
series of genes that occupy a specific
position on a specific chromosome.
Many genes have more than two possible alleles
A dominant gene is represented by a capital R.
A recessive is by a lowercase r. RR, rr, Rr
Recessive and Dominant Inheritance
Both parents carry a normal gene (N), and a faulty, recessive gene (n). The parents, are
unaffected by the faulty gene. Their offspring are either affected, unaffected, or carriers.
One parent has a single, faulty dominant gene (D), which overpowers he normal one (d),
affecting that parent. When the affected parent mates with an unaffected and non-carrier
mate (dd), the offspring are either affected or unaffected, but they aren’t carriers.
Sex linked (x-linked) is represented with XR, or Xr, or The alleles for sex-linked traits
are written as superscripts of the X or Y chromosome.

The top genotype is the father’s and the bottom is from
the mother
A
a
A AA Aa
a Aa
aa
A a
A Aa Aa
a Aa Aa
A
a Aa
Aa
a
a
aa
aa
Heterozygous dominant
Homozygous recessive
Homozygous dominant
The Punnett square shows that there is a
25% chance that a child will have the AA
genotype, a 50% chance of having the Aa
genotype and being a carrier of cystic
fibrosis, and a 25% chance of having the
aa genotype, which means that the child
will inherit the disease.

homozygous dominant: heterozygous dominant: homozygous recessive
A
a
A AA Aa
a Aa aa
o Ratios:
o1:2:1
1 (AA), 2 (Aa), 1 (aa)
oPercentages:
o 25%, 50%, 25%
25% (AA), 50% (Aa), 25% (aa)
o‘A’ represents the dominant allele
CFTR (cystic fibrosis
transmembrane conductance
regulator) and ‘a’ represents the
mutated CFTR that can cause cystic
fibrosis

A
A AA Aa
a Aa
Phenotype and Genotype
 AA: doesn’t not have cystic fibrosis (not a
carrier)



Homozygous dominant
Aa: doesn’t have the disease (carrier)

Heterozygous recessive
aa: the person has cystic fibrosis (carrier)

Homozygous recessive
a
aa
-Phenotype
- Ratios- 3 pink: 1 white
- Percentages- 75% pink: 25% white
A
a
A AA Aa
-Genotype
-Ratios- 1AA: 2 Aa: 1 aa
- Percentages- 25% AA: 50% Aa: 25% aa
a Aa
aa
A
AA
A
Aa
a
a
a
a
Genotype:
Ratio: 1AA: 2Aa: 1aa
Percentage: 25%AA:
50%Aa: 25%aa
Phenotype:
Ratio: 3 Pink: 1
white
Percentage: 75%
Pink: 25% White
- female
-male
White- person is
fine
Pink- person is
affected and has
2 “bad” genes