Genetic Testing

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Genetic Testing

• How can doctors test for genetic defects?

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Definition

• Process which involves examining individuals'
  genetic material for the presence an abnormality.
• Genetic testing can help determine if an
  individual is at risk for developing a certain
  disease.
• Just because a disease is caused by defective
  chromosomes, DNA, etc., it does not mean that the
  disease is hereditary.

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Karyotypes

• Karyotyping is a test used to examine chromosomes
  in a sample of cells which can help identify
  genetic problems as the cause of a disorder or
  disease. This test can
• Count the number of chromosomes
• Look for structural changes in chromosomes

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• The test can be performed on a sample of blood,
  bone marrow, amniotic fluid, or tissue from the
  placenta.
• To test amniotic fluid, an amniocentesis is done.

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• A bone marrow specimen requires a bone marrow
  biopsy.

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• A placenta sample requires a procedure known as
  chorionic villus sampling.

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• The sample of cells are placed into a dish and
  then grown.
• A sample is taken, stained and photographed.

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Down Syndrome (trisomy 21)
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Deletions

• An interstitial deletion is a deletion in the
  MIDDLE of the chromosome (see picture).
• A terminal deletion is a deletion at the END of a
  chromosome.

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Interstitial Deletion
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Ring 22 (muscle weakness, mental retardation,
lack of coordination)
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Cri-du-Chat Syndrome

• Terminal deletion on chromosome pair 5. In 80
  of cases, the defected chromosome comes from the
  sperm.
• Effects
• Small head
• Respiratory problems
• Underdeveloped larynx (cat like cry)
• Round face
• Small chin
• Heart defects
• Vision and/or hearing problems
• Hyperactivity and/or aggression
• Poor muscle tone

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Translocation Chromosomes 5 and 8