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

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.

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  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 151-155

  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 10-20 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 • 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? • 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.

  26. 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.

  27. 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?

  28. 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.

  29. 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

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