1. 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?

2. 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.

3. HUMAN GENETIC DISORDERS
CLASS NOTES – PAGES

4. What is a Genetic Disorder?
Abnormal condition that a person inherits through genes or chromosomes

5. What causes a genetic disorder?
1. Mutations:
Changes in a person’s DNA
2. Or the overall structure or number of chromosomes

6. 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.

7. 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?

8. 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

9. 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

10. 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

11. A day in the life..

12. 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)

13. 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.

14. 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

15. What is Anemia?
Unlike normal blood cells that last for about 4 months, sickle cells break down after days.
This causes anemia:
When the RBC’s count falls below normal.
Person feels weak and tires more easily

16. 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…

17. 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%

18. Symptoms of DMD Fatigue Muscle weakness Progressive difficulty walking
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.

19. A day in the life…

20. 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

21. 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

22. Cures for Hemophilia? A Day in the Life…
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…

23. 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

24. A day in the life…

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

28. 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.

29. 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?

31. 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.

32. 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