2. Human Genetic Disorders Two Types: Autosomal Recessive Disorder – Most common type, only shows in the phenotype when genotype is homozygous recessive Autosomal Dominant Disorder – These condition will appear in the phenotype when the genotype is heterozygous and homozygous recessive Polygenic Disorders – caused by multiple genes common examples are hypertension, diabetes, allergies, cleft lips, schizophrenia Pleiotropy – genes affect more than one characteristic can have physical and mental problems

3. Autosomal Recessive Disorders 1.Tay-Sachs – Chromosome 15 – Affects people of Jewish and Mediterranean descent. Lack of an enzyme causes a build-up of lipids in the lysosomes of brain cells. Death by age 3 or 4 years. 2.Cystic Fibrosis – Chromosome 7 – causes salty sweat and thick mucus in the lungs also affects the pancreatic duct so causes digestive problems. May live to 35 years 3.Phenylketonuria – Chromosome 12 – (Black urine disease) Missing an enzyme to metabolize phenylalanine an amino acid. This cause problems with brain development during first seven years if not controlled. Cannot digest artificial sweetener Nutrasweet. 4.Sickle Cell Anemia –Chromosome 11 – Red blood cells collapse in low oxygen level taking on a sickle shape. Leads to anemia, weakness, fever, spleen damage, kidney failure due to clots. Heteozygous condition will give immunity to malaria.

4. Autosomal Dominant Disorders – Usually passed on to children before symptoms start in parents 1.Neurofibromatosis – Chromosome 17 - (called Von Recklinghausen) develop large brown spots on skin that develop into tumors and cancer. 2. Huntington's Disease – Chromosome 4 – Appear normal until middle age 30-35 years then a progressive degeneration of brain tissue develops until death in 10 to 15 years. 3. Achrondroplasia – Chromosome 4 – Dwarfism only affects long bone development AA lethal, Aa dwarf, aa no problems

5. Multiple Alleles – Many genes competing for two loci on the chromosomes. The result may be codominance Example : Blood Types A = I a I a or I a i B = I b I b or I b i AB = I a I b (codominant condition) O = ii

6. Rh factors – Named after Rhesus Monkeys – Seven factors these are proteins on the surface of the RBCs – If you have 1 or more factors you are + no factors you are -