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Chromosomal Disorders Hawler Medical University, Iraq Bashdar Mahmud Hussen M.Sc. Biotechnology Bashdar Mahmud.

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Presentation on theme: "Chromosomal Disorders Hawler Medical University, Iraq Bashdar Mahmud Hussen M.Sc. Biotechnology Bashdar Mahmud."— Presentation transcript:

1 Chromosomal Disorders Hawler Medical University, Iraq Bashdar Mahmud Hussen M.Sc. Biotechnology Bashdar Mahmud Hussen M.Sc. Biotechnology

2 Genetic diseases traditionally - 3 types of diseases 1. genetically determined 2. environmentally determined 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) 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 1.No. of genes on chromosome 21 2.Mosaic Down syndrome 3. Causes of trisomy 4. Maternal age

6 Less frequent disorders Trisomy 18 (Edwards syndrome) 1: % (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 Monosomy 2. X-Chromosome Mosaicism 3. 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

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

12 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)

13 partial monosomy 1.proximal deletion (near to centromer) 2.interstitial deletion 3.subtelomeric deletion

14 It occurs during meiosis between misaligned homologous chromosomes (unequal crossing-over)unequal crossing-over Duplications of oncogenesoncogenes

15 Robertsonian translocationNon Robertsonian translocation or

16 fertility problems.

17 causes Turner syndromeTurner syndrome two identical arms

18 Chromosome Mutation Animation


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