Down's syndrome(Trisomy 21)
Trisomy 21 is d most frequen autosomal(chromosomal) syndrome.
1)Inclusion of an additional chromosome, trisomy 21 (95%) - 47 instead of 46 chromosomes
2)Chromosomal translocation defect specialy ocuring in young. Der is transfr of a segment of 1 chrmsome 2 a diffrent site of d same chromsom.
Incidence- 1 in 600
Diagnosis-
*Genral apearnc: craniofacial abnrmlities includ brachycephaly, upwards & outwards slanting of d eyes wid epicanthic folds. Short uper lip wid smal mouth & macroglossia. Baby's face resembles dat of d mangolian race. Hands r short & broad wid a single palmar crease. Der is increased association of cong heart disease (V.S.D), omphalocoele, cataracts, & duodenal atresia. Affected baby is mentaly retarded.
*Confirmation is by chromosomal analysis (karyotype) using bone marrow aspiration or leukocyte culture.
Genetic counselling in subsequent pregnancy.
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