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Chromosomal Disorders

Chromosomal Disorders. Bashdar Mahmud Hussen M.Sc. Biotechnology. Hawler Medical University, Iraq bashdar@res.hmu.edu.iq bmhscience@yahoo.com. Genetic diseases. traditionally - 3 types of diseases 1. genetically determined 2. environmentally determined 3. 1. + 2.

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Chromosomal Disorders

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  1. Chromosomal Disorders Bashdar Mahmud Hussen M.Sc. Biotechnology Hawler Medical University, Iraq bashdar@res.hmu.edu.iq bmhscience@yahoo.com

  2. Genetic diseases traditionally - 3 types of diseases 1. genetically determined 2. environmentally determined 3. 1. + 2. about 50% of spontaneous abortuses have chromosomal aberration • hereditary= derived from parents • familial = transmitted in the gametes through generations • congenital = present at birth (not always genetically determined

  3. Numerical abnormalities • euploidy - normal 46 (2n) • polyploidy (3n or 4n) - spontaneous abortion • Aneuploidy (whole chr. Missing or extra • trisomy (2n+1) - 47 - compatible with life • monosomy (2n-1) - autosomal - incompatible with life • - sex chromosomal - compatible with life

  4. Numerical Abnormalities • Trisomy 21 (Down syndrome) • Trisomy 18 • Trisomy 13 • Klinefelter Syndrome • Turner Syndrome • Triple X Syndrome • Most common chromosome abnormalities in aborted fetuses is: • Turner syndrome (45,X) • triploidy • trisomy 16

  5. No. of genes on chromosome 21 • Mosaic Down syndrome • 3. Causes of trisomy • 4. Maternal age

  6. Less frequent disorders • Trisomy 18 (Edwards syndrome) 1:6000 • 95% (extra number), 5% (translocation) • 90% of infants die • Trisomy 13 (Patau syndrome) 1:10000 • They have cleft lip and palates, extra fingers and toes, malformed and rotated internal organs

  7. Klinefelter Syndrome • Found only in males (47, XXY most common) • I in 500 males • Nondisjunction of XX homologues • Sterility • Testicular atrophy

  8. Turner Syndrome • Found in women with unmistakably female appearance • Absence of ovaries (gonadal dysgenesis) • Usually (45, X) missing one X chromosome 1. X-Chromosome Monosomy2. X-Chromosome Mosaicism3. X-Chromosome Defects ( small or large deletion)

  9. Triple X syndrome • 1 in 1,000 girls are born with Triple X syndrome • Menstrual irregularity • Delayed speech & language skill • A mosaic form also occurs where only a percentage of body cell contain XXX • not inherited

  10. Prenatal diagnostics • amniocentesis - analysis of amniotic fluid • cytogenetic analysis (karyotype) • analysis of various specific genes (PCR)

  11. Structural Abnormalities • May involve one or more chromosomes • Usually result from chromosome breakage • The effects of structural changes depend on their size & location loss of chromosomal material is more dangerous than gain abnormalities of sex chromosomes are better tolerated than autosomal, abnormalities of sex chromosomes sometimes symptomatic in adult age (e.g. infertility)

  12. partial monosomy • proximal deletion (near to centromer) • interstitial deletion • subtelomeric deletion

  13. It occurs during meiosis between misaligned homologous chromosomes (unequal crossing-over) Duplications of oncogenes

  14. Non Robertsonian translocation or Robertsonian translocation

  15. fertility problems.

  16. two identical arms causes Turner syndrome

  17. Chromosome Mutation Animation

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