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Genetic and Congenital Disorders

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Genetic and Congenital Disorders Powered By Docstoc
					Genetic and Congenital
      Disorders


          Unit One
          Chapter Four
Single Gene Disorders

   Allele

   Homozygous

   Heterozygous

   Genotype

   Phenotype
Autosomal Dominant
Disorders

   Males and females equally affected

   If parents don’t have the trait, the children won’t

   50% transmission

   No skipping of generations
    –   Penetrance
    –   Expressivity
Autosomal Dominant
Disorders

   Marfan’s syndrome
    –   Connective tissue disorder

    –   Manifested in the eyes, skeleton and
        Cardiovascular system
            Retinal detachment
            Long thin body
            Aortic dissection
Autosomal Dominat
Disorders

   Familial Hypercholesterolemia
    –   Premature coronary artery disease (CAD)

    –   Strong family history of CAD
            Multiple Myocardial Infarctions in 3rd and 4th decade
            Adults with cholesterol levels >300mg/dl
            Children’s levels > 250mg/dl
Autosomal Recessive
Disorders

   Only manifested when both alless are
    affected
   If heterozygous then parent may be a carrier
    of the mutation
   Usually seen early in life
   Males and females equally affected
   25% transmission
   Consanguinity
Autosomal Recessive
Disorders

   Pheylketonuria (PKU)

    –   Enzyme defect
            Increased levels of phenylalanine in blood
            Profound mental retardation
            Special diet
Autosomal Recessive
Disorders

   Cystic Fibrosis

   Multisystem involvement
    –   Respiratory
    –   Pancreatic
    –   Gastrointestinal
X-linked disorders

   Disorders almost always linked to X chromosome

   Predominantly Recessive

   Mother to son mutation

   Mother to daughter carrier

   50% transmission
X- linked disorders

   Fragile X syndrome
    –   Mental retardation
    –   Typical phenotypic appearance
            Long face and mandible
            Large ears
            Macroorchidism
X-linked disorders

   Hemophilia A ( factor VIII deficiency)

   Lifelong tendency to hemorrhage
    –   Deep soft tissue bleeding and hemathrosis
Multifactorial Disorders

   Factors include genetic and environmental

   Threshold phenomenon

   Cleft Lip, congenital hip dislocation, pyloric
    stenosis.
Review

   You are educating a parent of a child with
    Familial hypercholesterolemia . How would
    you address..
    –   Probability of transmission
    –   Carrier status
    –   Skipped generations
Review

   Autosomal recessive disorders are
    heterozygous/ homozygous?

   X-linked disorders are passed mother to son
    / daughter

   How common is fragile X syndrome?
Chromosomal Disorders

   Mosaicism: Alteration in duplication

   Aneuploidy: Alteration in numbers
    –   Monosomy: Turners’s syndrome (45XO)
    –   Polysomy: Trisomy ( 13,18,21)
    –   Klinefelter’s ( XXY)
   Trisomy 21
    –   Downs Syndrome


   Most common cause of mental retardation
    –   IQ range 25-60


   Typical phenotypic features
Period of Vulnerability

   Orgnagenesis days 15-60 post conception

   Early environmental influences

   Each organ has a critical timeframe
Teratogenic agents

   An environmental agent that induces
    structural malformation, growth deficiency,
    and/or functional alterations
    –   Radiation
    –   Chemicals/Drugs
    –   Infectious agents
Clinical Tetralogy

   Prevention of malformation
    –   Fetal alcohol syndrome
    –   Folic acid
    –   Vaccinations
Review

   Turners syndrome is a monosomy/ polysomy
    condition.
   Folic acid can help prevent what type of
    defects?
   The surgeon general has suggested a save
    number of alcoholic drinks per day for a
    pregnant women. What is this number?