Transcript 10.1 MEIOSIS INTERNET LESSON

11.1 GENETIC DISORDERS
BACKGROUND 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 disorder
he CONCLUDED:
-dark urine inherited by biochemical abnormality
enzyme 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 birth
CAUSE:
-Missing enzyme -- breaks down amino acid phenylalanine
EFFECT/PREVELENCE:
-excess phenylalanine
-mental deterioration
-1 in 10,000
TREATMENT:
Lifelong diet that limits protein
CYSTIC FIBROSIS
*excessive mucus production
CAUSE:
-defective gene that codes for membrane protein
EFFECT/PREVELENCE:
-chloride ions not absorbed in cells
-water does not diffuse from cells
-digestive & respiratory failure
-1 in 3,500 in US
TREATMENT:
-NO cure
-pancreatic enzyme supplements
-mucus thinning drugs
-daily cleaning of mucus from lungs
-physical therapy
ALBINISM
*lack of pigment/coloring in features
CAUSE:
-genes do not produce normal amounts of pigment--melanin
EFFECT/PREVELENCE:
-white hair
-pale skin
-pink pupils
-TREATMENT:
-NO cure
-protect skin from sun
-visual rehab
ALBINISM
www.positiveexposure.org
ALBINISM
www.positiveexposure.org
ALBINISM
www.positiveexposure.org
GALACTOSEMIA
CAUSE:
-absence of gene -- codes for enzyme that breaks down galactose
into lactose/glucose necessary for energy
EFFECT/PREVELENCE:
-mental disabilities
-enlarged liver
-kidney failure
1 in 50-70 thousand
CURE:
-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
-1/2500
CURE:
-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 life
CAUSE:
-gene affecting neurological function is defective
EFFECT/PREVELENCE:
-decline of mental/neurological functions
-ability to move deteriorates
-uncontrollable movements
-1 in 10,000
CURE:
NO cure or treatment
ACHONDROPLASIA
*dwarfism
CAUSE:
-gene that affects bone growth is abnormal
EFFECT/PREVELENCE:
-short arms/legs
-large head
-1 in 25,000
CURE:
-NO cure
ACHONDROPLASIA
DOMINANT GENETIC DISORDER
IDENTIFY
Which is more common—dominant or recessive
disorders?
-recessive
GENETIC DISORDERS
ANALYZE
Why 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