Autosomal Recessive Conditions

2. Phenylketonuria (PKU)• lack an enzyme to process phenylalanine amino acid• build up of PHE in urine and blood

causes mental deficiencies, motor problems• blood test at birth to identify PKU babies• specialized PHE-free formula• warnings on foods made with aspartame

3. Cystic Fibrosis: (CF)• 1 in 2500 Caucasian births• 1 in 25 Caucasians is a carrier• severe lung congestion (mucus),

frequent lung infections• ineffective pancreas no digestion

or absorption of most nutrients• abnormal liver function

1. Albinism• no melanin (pigment) in hair, eyes, skin• high risk of skin cancer• very poor vision

4. Tay-Sachs• lysosomes in brain cells lack enzyme to digest lipids• lipids accumulate in brain tissue cells swell, die• degeneration of nervous system• high allele frequency in European Jewish population • 1 in 25 Jewish Americans are carriers of allele• pre-natal screening; carriers have 50% of enzyme• very few Tay-Sachs babies born to Jewish parents

5. Sickle Cell Anemia • defective hemoglobin gene: 1 nucleotide

is wrong, 1 amino acid is incorrect• RBC’s will turn sickle shape under low O2

conditions• block blood vessels, very painful• 1 in 10 African Americans is a carrier of

the gene

Autosomal Dominant Conditions1. Huntington’s Disease:

• central nervous system problem

• make too much Huntington protein damages brain cells

• dementia, balance problems, delusions

• symptoms begin ~ 40 years of age

• child of Huntington’s parent has 50% chance of getting it

2. Marfan Syndrome:

• defect with fibrilin (in connective tissue of heart, eye and long bones)

• tall, thin, long arms and legs, long, slender fingers, enlarged aorta

3. Achondroplasia:

• defects in growth of long bones

• dwarfism short arms and legs but normal torso

• large head (compared to body)

• all are hybrid (AA is lethal)

Sex-Linked Recessive Conditions

1. Hemophilia• inability to clot blood • lack normal gene for clotting factor 8 protein)• injections of clotting factor 8 after cut or injury• clotting factor protein genetically engineered in bacteria• person may bleed to death from minor cuts, bruises• HIV contamination of clotting factor in early 80’s

2. Muscular Dystrophy • progressive muscle wasting• defect in dystrophin protein• abnormal dystrophin causes muscle cell membranes

to rupture during contraction muscle degeneration• onset of symptoms around 4 wheelchair by 12

cardiac muscle gives out by 20 patient death

Non-disjunction Conditions1. Down’s Syndrome = Trisomy 21• short, stocky body, wide neck, mental

deficiencies, large tongue• Non-disjunction in egg OR

translocation of #21 onto #14

2. Edward’s Syndrome = Trisomy 18• motor problems and mental deficiencies• congenital heart disease• death often in infancy

3. Patau’s Syndrome = Trisomy 13• cleft lip and palate• polydactyly (extra digits)• microencephaly (small head)

4. Cri-du-chat• deletion of piece of chromosome #5• “cat-like” cry• severe mental and physical abnormalities

5. Turner’s Syndrome: XO• short stature, wide neck• lack ovary development (sterile)• narrow aorta

6. Klinefelter’s Syndrome: XXY• male with lowered fertility, some breast development• long legs, short torso, wide hips• sparse facial and chest hair• other forms are: XXXY and XXXXY• additional X’s increase severity of phenotype

7. Super Male: XYY• 1 in 1000 male births• usually tall• extra testosterone• most XYY males do not know

their genotype

8. XXX: Trisomy X• most cases are normal, slight increase in sterility