Important Genetic Important Genetic DisordersDisorders

BioBio

DefinitionsDefinitions

►AutosomesAutosomes- any chromosome that is - any chromosome that is not a sex chromosome. Not the “X” or not a sex chromosome. Not the “X” or “Y”“Y”

►Sex-linkedSex-linked- genes located on the sex - genes located on the sex chromosome. Usually on the “X”chromosome. Usually on the “X”

►Nondisjunction- Nondisjunction- A chromosome A chromosome mishap in meiosismishap in meiosis

Huntington’s DiseaseHuntington’s Disease

►Symptoms: Gradual Brain tissue loss in Symptoms: Gradual Brain tissue loss in middle age. middle age.

►Defect: Inhibitor of brain cell Defect: Inhibitor of brain cell metabolismmetabolism

►Autosomal/somatic dominateAutosomal/somatic dominate►1/10,000 1/10,000

Cystic FibrosisCystic Fibrosis

►Symptoms: Mucus clogs lungs, liver, Symptoms: Mucus clogs lungs, liver, pancreaspancreas

►Defect: Failure of chloride ion Defect: Failure of chloride ion transport mechanismtransport mechanism

►Autosomal recessiveAutosomal recessive►1/2080 whites most common disorder1/2080 whites most common disorder

Sickle Cell AnemiaSickle Cell Anemia

►Symptoms: impaired blood circulation, Symptoms: impaired blood circulation, organ damageorgan damage

►Defect: Abnormal hemoglobin Defect: Abnormal hemoglobin molecules – RBC’smolecules – RBC’s

►Autosomal RecessiveAutosomal Recessive►1/500 African Americans -If 1/500 African Americans -If

heterozygous will not get malariaheterozygous will not get malaria

Tay-Sachs DiseaseTay-Sachs Disease

►Symptoms: deterioration of CNS in Symptoms: deterioration of CNS in infancy.infancy.

►Defect: Defective form of enzyme Defect: Defective form of enzyme hexosaminidase A (Hex A)hexosaminidase A (Hex A)

►Autosomal recessiveAutosomal recessive►1/1600 Jews of European descent1/1600 Jews of European descent

Phenylketonuria (PKU)Phenylketonuria (PKU)

►Symptoms: Failure of brain to develop Symptoms: Failure of brain to develop in infancy; if untreated causes death.in infancy; if untreated causes death.

►Defect: defective form of enzyme Defect: defective form of enzyme phenylalanine hydroxylasephenylalanine hydroxylase

►Autosomal recessiveAutosomal recessive►1/18,000 urine test, treated by diet 1/18,000 urine test, treated by diet

until puberty.until puberty.

HemophiliaHemophilia

►Symptoms: failure of blood to clotSymptoms: failure of blood to clot►Defect: defective form of blood-Defect: defective form of blood-

clotting agent.clotting agent.►X-linked recessiveX-linked recessive►1/7,0001/7,000

Muscular DystrophyMuscular Dystrophy

►Symptoms: wasting away of muscles; Symptoms: wasting away of muscles; short life expectancyshort life expectancy

►Defect: muscle fiber degenerateDefect: muscle fiber degenerate►X-linked recessiveX-linked recessive►1/10,000 “Jerry’s Kids”1/10,000 “Jerry’s Kids”

Down’s SyndromeDown’s Syndrome

►Symptoms: Mental retardation with Symptoms: Mental retardation with abnormal physical features.abnormal physical features.

►Defect: extra “X” chromosomeDefect: extra “X” chromosome►Non-disjunction of the 21Non-disjunction of the 21stst pair of pair of

chromosomes chromosomes ►Somatic chromosome Somatic chromosome ►Also called Trisomy 21Also called Trisomy 21

Klinefelter’s Klinefelter’s

►Symptoms: only in males, sterile, do Symptoms: only in males, sterile, do not develop 2not develop 2ndnd sex characteristics. sex characteristics. Below normal intelligenceBelow normal intelligence

►Defect: extra “X” in 23 pair of Defect: extra “X” in 23 pair of chromosomeschromosomes

►Meiosis error- genotype XXYMeiosis error- genotype XXY

Turner’s Turner’s

►Symptoms: only in females, appear Symptoms: only in females, appear normal at birth, become stockier & normal at birth, become stockier & shorter than other females- large necks, shorter than other females- large necks, sex organs & breasts do not develop- sex organs & breasts do not develop- sterilesterile

►Defect: missing “X” chromosome in 23Defect: missing “X” chromosome in 23rdrd pairpair

►Non-disjunction of sex chromosomeNon-disjunction of sex chromosome►Genotype XOGenotype XO