Genetic Disorders,
Pedigrees, and
Advances in
Genetics
Review…
Pattern baldness is sex-linked.
If a carrier female marries a pattern-bald man,
what are the chances of their children having
pattern baldness? Show the Punnett Square.
Use XB
XB
Y
X
XXB
XY
XB
XBXB
XBY
There would be a 2/4 chance that the
child would have pattern baldness.
Genetic Disorders
A
genetic disorder is an abnormal
condition that a person inherits
through genes or chromosomes.
 Some
genetic disorders are caused
by mutations in the DNA of genes.
 Other disorders are caused by
changes in the overall structure or
number of chromosomes.
Cystic Fibrosis
 Cause-
Recessive allele on Chromosome 7
 How
do people get the disorder?- The
recessive allele has to be inherited from BOTH
parents. (Parents are Heterozygous)
 Symptoms Affects
the respiratory and digestive
systems.
 A protein does not work correctly so thick
sticky mucus is produced in excess.
 Coughing, wheezing, respirator illness,
weight-loss, salty tasting skin, infections
Cystic Fibrosis cont’d
 Diagnosis-
Sweat test, because people who have
the disorder have 2-5 times as much salt in sweat
as a normal person. Or Blood Sample
 Treatment-
No cure, but new treatments help
people live longer. Chest physical therapy helps
clear mucus, prevent infections, antibiotics, gene
therapy
 Incidence-
2,500 babies per year in US.
10 million people are carriers and do not know.
Sickle Cell
 Cause-
Recessive allele on Chromosome 11
 How
do people get the disorder?- The
recessive allele has to be inherited from BOTH
parents. (Parents are Heterozygous)
 Symptoms Prevents
oxygen from reaching organs
causing damage.
 Red blood cells are not a normal shape
 Frequent infections, red blood cells don’t
live as long, low red blood cell count
(anemia), Pain, delayed growth,
Sickle Cell cont’d
 Diagnosis-
Newborns are usually screened at birth
with a Blood Test
 Treatment-
Daily antibiotics, take folic acid, get
rest, drink plenty of water, avoid to much physical
activity, blood transfusions or bone marrow
transplant in extreme cases
 Incidence-
born in US.
1 out of every 500 African-Americans
Hemophilia
 Cause How
Recessive allele on the X-Chromosome
do people get the disorder?-
 Boys-
receive the X chromosome with the allele
from mom,
 Girls- receive the X chromosome with the allele
from mom and dad.
 Symptoms Blood
clotting disorder, so person will not
normally clot when cut.
 Deep bruises, prolonged bleeding, joint
pain/swelling, pain
Hemophilia cont’d
 Diagnosis-
Family history and tests during
pregnancy. Mild hemophilia isn’t usually
diagnosised until after a major event. Blood tests.
 Treatment-
No cure, drugs can help blood to clot,
blood transfusions, avoid inquiry, pressure or ice
packs can help slow bleeding, wear med-alert
bracelet.
 Incidence-
1 in 5,000 male births. About 400
babies born each year in US.
Down Syndrome
 Cause21)
Extra copy of chromosome 21 (trisomy
 How
do people get the disorder? During meiosis
the chromosomes get crossed and fail to
separate so the egg or sperm end up with an
extra copy. (Non-disjunction)
 Symptoms Distinct
facial features: flat face, small nose,
abnormally shaped ears, larger tongue,
increased risk for other health concerns
 Have trouble learning and communicating
compared to peers.
Down Syndrome cont’d
 Diagnosis-
Screening tests by looking for physical
characteristics or blood tests can be done on
pregnant women. Confirmed with a Karyotype.
 Treatment-
No cure, but physical and speech
therapy can help develop skills, some corrective
surgeries are done if there are other medical
conditions.
 Incidence-
1 out of every 800 to 1,000 babies.
 Mostly likely to occur due to mom’s egg and
most likely with older mothers.
Huntington’s Disease
 Cause-
Dominant allele on Chromosome 4
 How
do people get the disorder?- Dominant
pattern, so everyone who inherits the allele
has the disorder.
 Symptoms Affects
the part of the brain used for
thinking talking, reasoning, emotion and
movement.
 Symptoms start between 30-50 (or later)get
worse over time.
 Poor memory, depression, mood swings,
lack of coordination, twitching, difficulty
moving, speaking walking etc.
Huntington’s Disease cont’d
 Diagnosis-
Pregnant women can have testing
done to find out if the baby has the disease but
you cannot tell when the person will get sick.
 Treatment-
Treatments make the person
comfortable but do not cure the disease.
(Medicines or Therapies)
 Incidence-
1 out of 30,000 people in US.
Phenylketonuria (PKU)
 Cause-
Recessive allele on Chromosome 12
 How
do people get the disorder?- The recessive
allele has to be inherited from BOTH parents.
(Parents are Heterozygous)
 Symptoms Person
with PKU cannot break down an
amino acid so it will build up in the blood and
poison cells.
 Babies usually have no symptoms at first but
left untreated can develop severe brain
damage and other issues.
 Stunted growth, eczema, musty body odor,
small head, fair skin
PKU cont’d
 Diagnosis-
Newborns are screened at birth
with a Blood Test, so that treatment can
be started early
 Treatment-
Must eat a protein-free diet
and avoid phenylalanine in all foods
 Incidence-
1 out of every 15,000 babies
born in the US.
Pedigrees
A
tool used to trace the
inheritance of traits in humans.
 Chart
or family tree that can trace
the inheritance of a genetic disorder
or train in a family.
 Can show possibilities of children
inheriting traits or where certain traits
come from.
 Can be used to diagnosis
conditions/genetic disorders.
Pedigree Symbols

Circle represents - Female

Square represents- Male

Horizontal line represents- marriage

Vertical line and bracket represents- connect
parents to children

Shaded all the way represents- person has the trait

Not shaded represents- person does not have the
trait

Shaded half-way represents- person is a carrier of
the trait
A Family Puzzle
Joshua and Bella Kimax have a son named
Ian. Ian has been diagnosed with the
recessive genetic disorder, cystic fibrosis.
Joshua and Bella are both healthy. Bella’s
parents (Paul and Bev) are both healthy.
One of Joshua’s parents (Steve and Erica)
is not healthy. Joshua’s sister, Sara, has
cystic fibrosis. Bella is an only child. Use
this information to make a pedigree for the
Kimax family. HINT: Start with Ian and his
alleles.
What
were the genotypes of
Joshua’s parents?
What are the genotypes of
Bella’s parents?
 Joshua
also has a brother. What is
the probability that he has cystic
fibrosis? Explain/ Show the Punnett
Square.
 Review the pedigree that you just
studied. What data suggests that
the trait is not sex-linked? Explain
using the families names and
genotypes.
 Imagine
you are a genetic
counselor. A couple asks why
you need information about
many generations of their
families to draw conclusions
about a hereditary condition.
Write an explanation you can
give them.
A man and a woman marry. They have 5
children, 2 girls and 3 boys. The mother is a
carrier of hemophilia, an X-linked disorder.
She passes the gene on to two of the boys
who died in childhood and one daughter is also
a carrier. Both daughters marry men without
hemophilia and have 3 children each (2 boys
and a girl). The carrier daughter has one son
with hemophilia. One of the non-carrier
daughter’s sons marries a woman who is a
carrier and they have twin daughters. What is
the percent chance that each of the twin
daughters will be a carrier.