Genetic Disorders Mrs Jacobs Unit 6 Genetic Abnormalities

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/bi ointeractive/dna/animati ons. 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