Transcript human genetic disorders - Conackamack Middle School

IN
• Today we will be studying several common
genetic disorders inherited by humans.
– How do you think a FAMILY is impacted when
a child in the family is diagnosed with a
genetic disorder?
– What types of changes in the household will
they need to make?
– What types of changes in their daily lives
could occur?
OUT
• Cystic Fibrosis is a recessive genetic disorder.
During routine blood work tests, a pregnant
woman found out she is a carrier for cystic
fibrosis. Her husband then had his blood tested
and he is ALSO a carrier for cystic fibrosis.
(Neither parent knew this information before.)
– If you were her obstetrician (baby doctor) how would
you explain the results to this woman.
– What probabilities would you tell this worried couple?
– Use a Punnett Square to support your answer.
HUMAN GENETIC
DISORDERS
CLASS NOTES – PAGES 151-155
What is a Genetic Disorder?
• Abnormal condition
that a person inherits
through genes or
chromosomes
What causes a genetic disorder?
1. Mutations:
– Changes in a person’s
DNA
2. Or the overall
structure or number
of chromosomes
Who can get genetic disorders?
• Anyone
– Parents could be carriers for a
disorder and pass it on to their
children
OR
– The disorder could happen by chance
with no reason whatsoever.
• Symptoms of the disorder could be
seen prenatally (pre-birth), at
birth, not be seen into childhood or
in rare cases, not be seen until
adulthood.
We will examine several genetic
disorders.
• We will look for the
following information:
– How is the disorder inherited?
– What are the characteristics
of someone who has inherited
this disorder?
– What are the treatments for
someone who has inherited
this disorder?
Examples of Human Genetic
Disorders
• Cystic Fibrosis
– Caused by a recessive
allele on one chromosome
– Affects the body’s ability
to move salt and water in
and out of the cells
– Thick mucus forms in the
lungs and intestines
– Makes it difficult for
that person to breathe
Cystic Fibrosis (CF)
• About 3,000 babies are
born each year with
cystic fibrosis
• More than 10,000,000
healthy people are
unknowingly carriers of
this disorder
• Each time 2 carriers
conceive there is a 25%
chance that their child
will have CF
Cures for CF?
• There are NO cures for
CF, but there are
treatments
• Patients can have
breathing treatments
administered
• Chest therapy must be
done each day to clear the
mucus from their lungs
A day in the life..
Sickle Cell Anemia
– Affects the blood
– People with the disease form
an abnormal type of
hemoglobin (the part of the
blood that carriers oxygen)
– They suffer from lack of
oxygen and experience pain
and weakness (called a
sickle-cell crisis)
Sickle Cell Anemia
• Sickle-cell Disease
– A co-dominant trait.
Person must inherit
BOTH alleles for the
disease to have it.
– A person with one of
the alleles will produce
BOTH types of cells
but will not show signs
of the disease.
Sickle-Cell Disease
• More than 70,000
Americans have
sickle-cell disease
• Affects people mostly
of African ancestry
• 1 in 12 African
Americans are
CARRIERS for the
disorder
What is Anemia?
• Unlike normal blood cells
that last for about 4
months, sickle cells
break down after 10-20
days.
• This causes anemia:
– When the RBC’s count
falls below normal.
– Person feels weak and
tires more easily
Cures for Sickle-Cell Disease?
• There are No cures for sicklecell disease, but there are
several forms of treatment
– Blood transfusions
– Antibiotics
• Penicillin starting from 2
months old
– Proper nutrition, bedrest,
protection against
infection, avoidance of
extreme cold and extreme
hot temperatures
A day in the life…
Duchenne Muscular Dystrophy
• Involves muscle weakness that
gets worse over time.
• A defective gene causes the
person to not make a protein
called dystrophin
• Recessive Sex-linked trait
– Males are more likely to inherit
this disorder than females.
• Occurs in approximately 1 out
of 3600 male infants
50%
50%
50%
50%
Symptoms of DMD
• Fatigue
• Muscle weakness
– Begins in the legs and pelvis, but also occurs less
severely in the arms, neck, and other areas of the body
– Difficulty with motor skills (running, hopping, jumping)
– Frequent falls
– Rapidly worsening weakness
• Progressive difficulty walking
– Ability to walk may be lost by age 12
• By age 10, the person may need braces for
walking. By age 12, most patients are confined
to a wheelchair.
A day in the life…
Examples of Genetic Disorders
• Hemophilia
– Affects the blood
– People with the disorder do
not have blood that
properly clots, they are
missing a clotting factor
– Left untreated, people with
the disease could bleed to
death from a cut or gash
– Sex-linked trait: Recessive
allele carried on the X
chromosome
Hemophilia
• There are
approximately 20,000
hemophilia patients in
the United States
(400,000 world wide)
• About 400 babies are
born each year with
the disorder
• Symptoms include
large bruises, swelling
in the joints, and
internal bleeding
Cures for Hemophilia?
A Day in the
• There are no cures for
the disorder.
Treatments include:
– replacing the missing
clotting factor in the
blood. This is done by
injecting a product
that contains the
needed factor into a
Bleeding stops
Life… vein.
when enough clotting
factor reaches the
affected area.
Examples of Human Genetic Disorders
• Down’s Syndrome (Trisomy
21)
– Extra copy of Chromosome
21
– Symptoms include:
• Facial defects
• Mental retardation
• Hearing/sight problems
• Heart defects
• Various infections
– Occurs in 1 out of every
1000 births
– Life expectancy is about
55 years old
A day in the life…
Pedigrees: a chart or family tree that
tracks which members of a family have a
particular trait.
Diagnosing Genetic Disorders
• Amniocentesis:
– Doctors use a long
needle to remove some
fluid from around the
baby
– They test the fluid for
genetic disorders
because the fluid
contains cells from the
baby
– From that test, a
karyotype is created.
What is a karyotype
• A picture of all
the chromosomes
in a cell.
• Reveals whether
the person has
the correct
number of
chromosomes in
their cells.
Is this a karyotype of a
male or female? How do
you know?
Genetic Counseling
Pregnant women will have many prenatal tests done while pregnant.
• These tests will look at the blood work,
urine analysis, diet and overall health of
the mother to determine protein levels,
blood production, chromosomal number,
etc. in the fetus.
If the medical tests on the mother suggest
more genetic testing, than the couple may
be referred to a genetic counselor.
•Someone who works with the medical team to
help families who are risk for having offspring
with genetic disorders.
Role of the genetic counselor…
• evaluating family
history and medical
records
• ordering genetic tests
• evaluating the results
of this investigation
• helping parents
understand and reach
decisions about what
to do next