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Today we will be studying several common genetic disorders inherited by humans.

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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?

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  • 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?
  • 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



what is a genetic disorder
What is a Genetic Disorder?
  • Abnormal condition that a person inherits through genes or chromosomes
what causes a genetic disorder
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
Who can get genetic disorders?
  • Anyone
    • Parents could be carriers for a disorder and pass it on to their children


    • 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 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
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
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
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
sickle cell anemia
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 anemia1
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
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
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
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…

duchenne muscular dystrophy
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





symptoms of dmd
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.
examples of genetic disorders
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
  • 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
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…

examples of human genetic disorders1
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
diagnosing genetic disorders
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
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
Genetic Counseling

Pregnant women will have many pre-natal tests done while pregnant.

If the medical tests on the mother suggest more genetic testing, than the couple may be referred to a genetic counselor.

  • 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.
  • Someone who works with the medical team to help families who are risk for having offspring with genetic disorders.
role of the genetic counselor
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