1. Human Genetic Disorders
Biology

2. Genetic Testing Amniocentesis and Chronic Villi Sampling Karyotyping
Sample of amniotic fluid or placenta
Karyotyping
Taking a picture of the chromosomes in a cell

3. What Can Go Wrong? Nondisjunction (most deadly) DNA mutations
Improper separation of homologous chromosomes in meiosis I or chromatids in mieosis II or mitosis (at an early embryonic stage)
Results in too many or too few chromosomes in daughter cells
DNA mutations
More specific letter-changes in code
Results in the inability to make certain proteins

4. Nondisjunction Causes:
Aneuploidy: cells that have too many or too few chromosomes are aneuploid.
Monosomy: only 1 of a pair present
Trisomy: 3 instead of 2 present

5. Incidence of Genetic Abnormalities
Maternal Age
At 25 years, 17% of eggs may have chromosomal abnormalities. At 40 years, up to 74% may contain abnormalities.
Spontaneous Abortion (Miscarriage)
Two-thirds of all pregnancies are lost. These miscarriages are called spontaneous abortions.
Genetic mutation causes an estimated 60% of these spontaneous abortions.

6. Family Pedigrees

7. Down Syndrome Caused by Trisomy 21 Symptoms: Mental retardation
Flattened face
Sparse, straight hair
Short stature
High risk of cardiac anomalies, leukemia, cataracts, and digestive blockages
Average life expectancy: 55 years (much longer than it used to be even just recently)

8. Edward Syndrome Caused by Trisomy 18 Symptoms:
Mental and physical retardation
Skull and facial abnormalities
Defects in all organ systems
Poor muscle tone
Average life expectancy: 2-4 months

9. Patau Syndrome Caused by Trisomy 13 Symptoms:
Mental and physical retardation
Skull and facial abnormalities
Defects in all organ systems
Cleft lip & large triangular nose
Extra digits
Average life expectancy: 6 months (but ½ die in the first month)

10. Sex Chromosome Abnormalities
Turners Syndrome (X0 - female)
1 in 2000
Infertile, sexually underdeveloped, short stature, narrow aorta, normal intelligence
Klinefelter Syndrome (XXY - male)
1 in 1000
Reduced sexual maturity, secondary sexual characteristics (breast swelling), no sperm production

11. Sex Chromosome Abnormalities
Triple X Syndrome (XXX – female)
1 in 1500
Slight IQ reduction, menstrual irregularities
Jacob Syndrome (XYY – male)
Incidence unknown (lack of diagnosis)
Tall, acne issues, speech/reading problems
Disproportionate number incarcerated
96% are normal (most don’t realize they have this condition)

12. DNA Mutations Cri du Chat Syndrome (cry of the cat) Fragile X
Deletion on part of chromosome 5
Fragile X
Repeated sequences of CCG on X chromosome
Normal = 6-50 copies
Carrier (males) = copies
Disorder = more than 230 copies
Causes mental retardation (2nd behind only Down Syndrome)

13. Autosomal Recessive Disorders
Cystic Fibrosis (CF)
Mutation on chromosome 7
Thick mucous develops in lungs and digestive tract
Difficulty breathing & lung infections
Most common lethal genetic disorder
1 in 25 is a carrier
1 in 2500 has disorder

14. More Autosomal Recessive
Tay Sachs Disease
Fatty substance builds up in neurons
Gradual paralysis and loss of nervous function by age 4-5
Single defective enzyme
Heterozygote carriers (Hh) do not have disorder, but are resistant to Tuberculosis
Especially common in Jewish population (central and eastern European descent), up to 11% are carriers

15. More Autosomal Recessive
PKU (Phenylketonuria)
Can’t break down amino acid phenylalanine (missing critical enzyme)
Phenylalanine builds up and interferes with nervous system leading to mental retardation and even death
Early screening  phenylalanine restricted diet for children with disorder

16. More Autosomal Recessive
Sickle-Cell Anemia
Abnormality in hemoglobin (carries oxygen in our red blood cells)
Cells become sickle-shaped and clog blood vessels (painful)
Causes poor circulation, jaundice, anemia, and hemorrhaging
Heterozygote carriers (Hh) do not have disorder and are resistant to malaria
8-10% of Africans (or descendants) are carriers

17. Sickle-Cell Anemia Photo

18. Autosomal Dominant Disorders
Neurofibromatosis (NF)
Could be “Elephant Man’s” disorder
As mild as tan spots on skin
Could cause severe deformities, tumors, even death
1 in 3000 newborns
Mutation on chromosome 17

19. Autosomal Dominant Disorders
Huntington’s Disease
Brain cells degenerate, causing involuntary muscle jerks, slurred speach, loss of balance, mood swings, memory loss, incapacitation
Progressive: eventually causes death
Onset: years old
Repeated sequences of AGC on chromosome 4
Diagnostic test available, but no cure
Would you want to know?

20. X-Linked or Sex-Linked Traits
Traits located on X Chromosome
Males have them more often than females
They only have one X chromosome

21. X-Linked or Sex-Linked Traits
Colorblindness (3 types – Red/Green most common)

22. X-Linked or Sex-Linked Traits
Hemophilia
1 in 1500 males
Lack a blood clotting factor
Can bleed to death from wounds or bruises (internal bleeding)
Duchenne Muscular Dystrophy
1 in 5000 males
Muscular deterioration starts 3-5 years old
Wheelchair by 12, rarely survive past 20