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11.1 GENETIC DISORDERSBACKGROUND INFORMATION(Early 1900s) Sir Archibald Garrod, British physician, discovered patterns of inheritance leading to alkaptonuria—-Alkaptonuria disorder: urine turns black/acid excretion/severe arthritis he NOTED: -ran in families, child could have it even if parents didn’t
recessive genetic disorderhe CONCLUDED:
-dark urine inherited by biochemical abnormalityenzyme deficiency
NEW VOCABULARY
Heterozygous parents with recessive allele for disorder—
___________carrier
RECESSIVE GENETIC DISORDER
RECESSIVE GENETIC DISORDERS— -individual is homozygous recessive--2 recessive alleles
disorder shown
INFER: -What are the chances for 2 carriers to have a child with a recessive genetic disorder?__________
25%
PKU-Phenylketonuria
*Identified at birthCAUSE:-Missing enzyme -- breaks down amino acid phenylalanineEFFECT/PREVELENCE:-excess phenylalanine -mental deterioration-1 in 10,000TREATMENT:Lifelong diet that limits protein
CYSTIC FIBROSIS
*excessive mucus productionCAUSE:-defective gene that codes for membrane proteinEFFECT/PREVELENCE:-chloride ions not absorbed in cells-water does not diffuse from cells-digestive & respiratory failure-1 in 3,500 in USTREATMENT:-NO cure-pancreatic enzyme supplements-mucus thinning drugs-daily cleaning of mucus from lungs-physical therapy
ALBINISM
*lack of pigment/coloring in featuresCAUSE:-genes do not produce normal amounts of pigment--melaninEFFECT/PREVELENCE:-white hair-pale skin-pink pupils-TREATMENT:-NO cure-protect skin from sun-visual rehab
GALACTOSEMIA
CAUSE:-absence of gene -- codes for enzyme that breaks down galactose into lactose/glucose necessary for energyEFFECT/PREVELENCE:-mental disabilities-enlarged liver-kidney failure1 in 50-70 thousandCURE:-NO cure-restricted diet of lactose/galactose-avoid milk products
Tay-Sachs Disease/TSD
*cherry red spot on back of eye CAUSE:-absence of necessary enzyme that breaks down fatty substances—gangliosides EFFECT/PREVELENCE: -affects people of Jewish descent-build up of fatty deposits in brain-mental disabilities -1/2500CURE:-NO cure-death by age 5
DOMINANT GENETIC DISORDER
DOMINANT GENETIC DISORDERS— -individual is homozygous dominant -OR- heterozygous
-disorder shown if a single dominant allele is present
HUNTINGTONS DISEASE
?think about-symptoms do not show up until later in lifeCAUSE:-gene affecting neurological function is defectiveEFFECT/PREVELENCE:-decline of mental/neurological functions-ability to move deteriorates-uncontrollable movements-1 in 10,000 CURE:NO cure or treatment
ACHONDROPLASIA
*dwarfismCAUSE:-gene that affects bone growth is abnormalEFFECT/PREVELENCE:-short arms/legs-large head-1 in 25,000CURE:-NO cure
ACHONDROPLASIA
DOMINANT GENETIC DISORDER
IDENTIFYWhich is more common—dominant or recessive disorders? -recessive
GENETIC DISORDERS
ANALYZEWhy are recessive disorders more prevalent? -if dominant trait interferes with survival, individuals are less likely to pass the gene to the next generation-when disorder is recessive, carriers do not display disorder—pass on wo/being aware
