Transcript H Biology Notes on Genetic Disorders teaching

Autosomal Recessive Conditions
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Albinism
no melanin (pigment) in hair, eyes, skin
high risk of skin cancer
very poor vision
Phenylketonuria (PKU)
lack an enzyme to process phenylalanine amino acid
build up of PHE in urine and blood
causes mental deficiencies, motor problems
blood test at birth to identify PKU babies
specialized PHE-free formula
warnings on foods made with aspartame
3. Cystic Fibrosis: (CF)
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1 in 2500 Caucasian births
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1 in 25 Caucasians is a carrier
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severe lung congestion (mucus),
frequent lung infections
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ineffective pancreas  no digestion
or absorption of most nutrients
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abnormal liver function
4. Tay-Sachs
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lysosomes in brain cells lack enzyme to digest lipids
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lipids accumulate in brain tissue  cells swell, die
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degeneration of nervous system
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high allele frequency in European Jewish population
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1 in 25 Jewish Americans are carriers of allele
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pre-natal screening; carriers have 50% of enzyme
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very few Tay-Sachs babies born to Jewish parents
5. Sickle Cell Anemia
• defective hemoglobin gene: 1 nucleotide
is wrong, 1 amino acid is incorrect
• RBC’s will turn sickle shape under low O2
conditions
• block blood vessels, very painful
• 1 in 10 African Americans is a carrier of
the gene
Autosomal Dominant Conditions
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Huntington’s Disease:
central nervous system problem
make too much Huntington protein damages brain cells
dementia, balance problems, delusions
symptoms begin ~ 40 years of age
child of Huntington’s parent has 50% chance of getting it
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Marfan Syndrome:
defect with fibrilin (in connective tissue of
heart, eye and long bones)
tall, thin, long arms and legs,
long, slender fingers, enlarged aorta
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Achondroplasia:
defects in growth of long bones
dwarfism  short arms and legs but normal torso
large head (compared to body)
all are hybrid (AA is lethal)
Sex-Linked Recessive Conditions
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Hemophilia
inability to clot blood
lack normal gene for clotting factor 8 protein)
injections of clotting factor 8 after cut or injury
clotting factor protein genetically engineered in bacteria
person may bleed to death from minor cuts, bruises
HIV contamination of clotting factor in early 80’s
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Muscular Dystrophy
progressive muscle wasting
defect in dystrophin protein
abnormal dystrophin causes muscle cell membranes
to rupture during contraction  muscle degeneration
onset of symptoms around 4  wheelchair by 12 
cardiac muscle gives out by 20  patient death
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Non-disjunction Conditions
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Down’s Syndrome = Trisomy 21
short, stocky body, wide neck,
mental deficiencies, large tongue
Non-disjunction in egg OR
translocation of #21 onto #14
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Edward’s Syndrome = Trisomy 18
motor problems and mental deficiencies
congenital heart disease
death often in infancy
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Patau’s Syndrome = Trisomy 13
cleft lip and palate
polydactyly (extra digits)
microencephaly (small head)
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Cri-du-chat
deletion of piece of chromosome #5
“cat-like” cry
severe mental and physical abnormalities
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Turner’s Syndrome: XO
short stature, wide neck
lack ovary development (sterile)
narrow aorta
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Klinefelter’s Syndrome: XXY
male with lowered fertility, some breast development
long legs, short torso, wide hips
sparse facial and chest hair
other forms are: XXXY and XXXXY
additional X’s increase severity of phenotype
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Super Male: XYY
1 in 1000 male births
usually tall
extra testosterone
most XYY males do not
know their genotype
XXX: Trisomy X
most cases are normal, slight increase in sterility
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