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Today we will be studying several common genetic disorders inherited by humans. - PowerPoint PPT Presentation

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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

Pedigrees a chart or family tree that tracks which members of a family have a particular trait
Pedigrees: a chart or family tree that tracks which members of a family have a particular trait.

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