Chromosomal Disorders Hawler Medical University, Iraq [email protected] [email protected]...
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Transcript of Chromosomal Disorders Hawler Medical University, Iraq [email protected] [email protected]...
Chromosomal Disorders
Hawler Medical University, [email protected]@yahoo.com
Bashdar Mahmud HussenBashdar Mahmud HussenM.Sc. Biotechnology
Bashdar Mahmud HussenBashdar Mahmud HussenM.Sc. Biotechnology
Genetic diseasestraditionally - 3 types of diseases1. genetically determined2. environmentally determined3. 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
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
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
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
Klinefelter Syndrome
• Found only in males (47, XXY most common)• I in 500 males• Nondisjunction of XX homologues• Sterility• Testicular atrophy
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)
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
Prenatal diagnostics
• amniocentesis - analysis of amniotic fluid• cytogenetic analysis (karyotype)• analysis of various specific genes (PCR)
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 gainabnormalities of sex chromosomes are better tolerated than autosomal, abnormalities of sex chromosomes sometimes symptomatic in adult age (e.g. infertility)
partial monosomy
1. proximal deletion (near to centromer)2. interstitial deletion3. subtelomeric deletion
It occurs during meiosis between misaligned homologous chromosomes (unequal crossing-over)
Duplications of oncogenes