Chromosome Disorders

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Chromosome Disorders
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Prenatal Diagnosis
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Amniocentesis

• A small sample of the amniotic fluid surrounding
  the baby is removed using a syringe.
• The fluid contains skin cells from the baby.
• The skin cells are grown in the lab.

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• The chromosomes from the cells are magnified
  under a microscope and a picture is taken.
• The chromosomes are cut out and arranged in
  homologous pairs in decreasing size order.
• This is called a karyotype.

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Down Syndrome (Trisomy 21)

• Extra chromosome 21 in
• every cell of the body
• Causes mental retardation, heart defects
• Karyotype 47,XX21 or 47,XY21

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• As a woman gets older, her chances of having a
  baby with a chromosome abnormality increases
• remember, a woman is born with all of her egg
  cells, but meiosis is not yet complete
• (egg development stops in prophase I until the
  follicle matures prior to ovulation)

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• Most cases of Down syndrome are caused by
  nondisjunction during meiosis
• Nondisjunction homologous chromosomes do not
  separate properly

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• http//www.mhhe.com/biosci/genbio/biolink/j_explor
  ations/ch10expl.htm

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Turner Syndrome45,X

• Characteristics
• short stature
• ovaries do not develop (infertile)
• cardiovascular problems
• kidney and thyroid problems
• skeletal disorders such as scoliosis

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Klinefelter Syndrome47,XXY

• Characteristics
• Infertility (cannot produce a lot of sperm)
• Learning disability

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Trisomy 13

• severe birth
• defects
• mental
• retardation

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Trisomy 18

• severe birth
• defects
• mental
• retardation