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27.3 Genetic Disorders

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					       27.3 Genetic Disorders
•Errors in the chromosome number
•Genetic Disorders and sex chromosomes
•Genetic Disorders and autosomes
•Genetic Counseling
Errors in Chromosome Numbers
• Less than 46 chromosomes
• OR
• More than 46 chromosomes

• Due to mistakes in meiosis
• Anaphase, chromosomes do not get
  pulled appart
Errors due to Meiosis



                                    4 Possible Gametes
                                       Sperm or Egg




*Normal   *Normal   *Too many   *Too few
                Trisomy
• Inheriting three copies of a chromosome
  instead of two
• Too many
• 47 chromosomes
             Down syndrome
• Outwardly slanted eyes
• Exaggerated fold of skin
  on the inside of the eye
• Flat ears set low on the
  head
• Flattened face
• Small teeth
• Relatively short arms and
  legs.
           Edward syndrome
• Defects of the kidneys,
  ureters, heart, lungs and
  diaphragm.
• Cleft lip or cleft palate.
• Small skull
  (microcephaly).
• Malformations of the
  hands and feet
• Neural tube defect, where
  the spinal cord, meninges
  and blood vessels
  protrude through a gap in
  the vertebrae
• Malformations of the sex
  organs
                 Patau syndrome
• Small skull (microcephaly).
• An abnormal opening in the skull.
• Malformations of part of the brain.
• Structural defects of the eyes.
• Cleft lip or cleft palate.
• Additional toes or fingers
• Congenital heart disorders, such as
  ventricular septal defect.
• Neural tube defect, where the spinal
  cord, meninges and blood vessels
  protrude through a gap in the vertebrae
• Malformations of the sex organs.
              Monosomy
• Inherit one copy of a chromosome instead
  of two
• Too few
• 45 chromosomes
      Monosomy Disorders
• Turner Syndrome
            Turner Syndrome
•   condition in females (XX)
•   Due to an absent X-chromosome
•   short stature
•   sexual underdevelopment
•   physical abnormalities
    Types of Chromosomes
1. Autosome: a non-sex chromosomes
   pairs 1 -22 on a karyotype

2. Sex chromosomes: the XX or XY
   pair 23 on a karyotype
         Genetic Disorders

Carried by Sex Chromosomes:
• Hemophilia

Carried by Autosomes
• Dyslexia
• PKU
             Hemophilia
• Disorder
• Blood can not form clots
• Found on recessive gene
                  Dyslexia
•   A learning disorder
•   Can not see or write letters and or words
•   Appear backwards
•   Dominant gene
                  PKU
• Body lacks the enzyme necessary to
  metabolize phenylalanine to tyrosine.
• Causes brain damage and progressive
  mental retardation
         Genetic Counseling
• Provide information and support to families
  who have members with birth defects or
  genetic disorders
• Or
• to families at risk for a variety of inherited
  conditions.
               Counselors
• They identify families at risk, investigate
  the problem present in the family, interpret
  information about the disorder, analyze
  inheritance patterns and risks of
  recurrence, and review available options
  with the family.
                Pedigree
• a diagram of family relationships that uses
  symbols to represent people and lines to
  represent genetic relationships.
• Determine the mode of inheritance
  (dominant, recessive, etc.) of genetic
  diseases.
                  Pedigree
• A series of symbols
  are used to represent
  different aspects of a
  pedigree.
                     Pedigree
Dominant traits:

• Never skips a generation

• Two affected individuals can give rise to unaffected
  individuals

Recessive traits:

• may skip a generation

• two unaffected individuals can give rise to affected
  individuals
   Marriage Line
                              I

Children line

                              II


                   Siblings

                              III




                              IV

				
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posted:6/20/2012
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