IN

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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?

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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.

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HUMAN GENETIC DISORDERS

• CLASS NOTES PAGES 151-155

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What is a Genetic Disorder?

• Abnormal condition that a person inherits through
  genes or chromosomes

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What causes a genetic disorder?

• 1. Mutations
• Changes in a persons DNA
• 2. Or the overall structure or number of
  chromosomes

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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.

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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?

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Examples of Human Genetic Disorders

• Cystic Fibrosis
• Caused by a recessive allele on one chromosome
• Affects the bodys 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

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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

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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

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A day in the life..
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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)

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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.

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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

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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 RBCs count falls below normal.
• Person feels weak and tires more easily

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Cures for Sickle-Cell Disease?

• There are No cures for sickle-cell 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
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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

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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.

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A day in the life
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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

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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

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Cures for Hemophilia?

• 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 vein. Bleeding
  stops when enough clotting factor reaches the
  affected area.

A Day in the Life
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Examples of Human Genetic Disorders

• Downs 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

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A day in the life
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Pedigrees a chart or family tree that tracks
which members of a family have a particular
trait.
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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.

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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?
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Genetic Counseling

• Pregnant women will have many pre-natal 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.

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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