Autosomal Abnormilities

• Autosomal chromosomal disorder caused by trisomy of chromosome 21.
• Affected individuals have 47 chromosomes instead of 46.
• Usually arises due to non-disjunction of autosomes during gamete formation.
• Risk is higher in older mothers (especially > 35 years) or with previous Down’s babies.
• Condition can be detected prenatally by amniocentesis.

• Extra copy of chromosome 21 → three copies (trisomy 21).
• Non-disjunction during meiosis produces a gamete with an extra autosome.
• Fusion of this gamete with a normal gamete forms a trisomic zygote.

Karyotype of Down’s syndrome:

• Intellectual disability / mental retardation (variable degree).
• Poor skeletal development; short, stocky body.
• Characteristic facial traits: flat, rounded face; small head; flattened nasal bridge.
• Habitually open mouth with a large protruding tongue.
• Eyes slant up and out with epicanthic skin folds.
• Flat broad hands, single palmar crease; short fifth finger.
• Often associated with congenital heart defects and low muscle tone.

Signs of Down's syndrome

• Amniocentesis can detect the condition during early pregnancy.
• No curative treatment is described; management is supportive, with medical care and parental support.

• Down’s syndrome is a chromosomal disorder caused by trisomy of chromosome 21.
• Affected individuals have 47 chromosomes instead of the normal 46 due to non-disjunction.
• It is characterised by mental retardation, distinctive facial features, and short stature.
• Congenital heart defects and low muscle tone are commonly associated features.
• The risk increases with advanced maternal age (above 35 years) and can be detected by amniocentesis.