1. Mrs. Jacobs Unit 6: Genetic Abnormalities IN 149
Genetic Disorders
Mrs. Jacobs
Unit 6: Genetic Abnormalities
IN 149

2. Autosomal Disorders
Autosome: any non-sex chromosome (cannot be X or Y chromosome)
There are 22 pairs in humans (23 pairs minus the sex chromosomes)
Example: Down Syndrome (DS)

3. Down’s Syndrome (DS) Excess # 21 chromosome
Prenatal testing can be done
Result of chromosomal mutation
1 in 900 people born with this
Likelihood of having a child with DS increases with advancing maternal age
Symptoms: mental retardation, upward slant to eyes, small mouth, abnormal ear shape, decreased muscle tone
No cure

4. Sex Chromosome Disorders
Disorders that occur on sex chromosomes (X or Y)
Examples:
Klinefelter’s Syndrome
Turner’s Syndrome

5. Klinefelter’s Syndrome
47, XXY
1 in 1000 male live births
Mild learning difficulties
Taller than average with long lower limbs
Show mild enlargement of breasts
Infertile (absence of sperm)
Treat with testosterone

6. Turner’s Syndrome 45, X Low incidence Look normal Ovarian failure
Normal intelligence
Short stature
Estrogen therapy

7. Single Gene Disorders Cystic Fibrosis Hemophilia Sickle Cell Anemia
Phenylketonuria

8. Cystic Fibrosis (CF) Recessive disorder
Mutation stops production of protein in lung cells, pancreas
Thick mucus, bacterial infections in lung
“sweat test”
Most common in Caucasians (1 in 3300)
Chest percussions, diet supplements
Shortened life expectancy

9. Sickle Cell Anemia Mutation in blood protein “sickle” shape to RBC
Screening tests
Most common in African-Americans (1 in 375)
Pain associated with blocked vessels, causes anemia (fatigue)
Common where mosquito-borne malaria is present
Animation:

10. Hemophilia Sex-linked Failure of blood to clot Rare in females
Injections with clotting factors to stop bleeding episodes
$350,000 a year in treatment

11. PKU Mutation disrupts function of enzyme
Leads to high phenylalanine levels in brain (poisons)
Mental retardation, epilepsy
Screening newborns (heel prick)
1 in 10,000 Caucasian births
Extremely rare in African-Americans
Look normal
Need low-protein diet, smelly formulas