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

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)

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

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

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

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

Single Gene Disorders Cystic Fibrosis Hemophilia Sickle Cell Anemia Phenylketonuria

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

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: http://www.hhmi.org/biointeractive/dna/animations.html

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

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