Question

Comment upon any three chromosomal aberrations (syndrome) found in humans.

Hint:

Remember: Down's = Trisomy 21, Turner's = 45, XO, Klinefelter's = 47, XXY. Easy to recall with numbers.

Answer 1

Chromosomal aberrations are structural or numerical changes in chromosomes that cause genetic disorders in humans. These may involve extra, missing, or altered chromosomes. Three common syndromes are: 1. Down's Syndrome (Trisomy 21): \[\begin{array}{rl} \bullet & \text{Caused by the presence of an extra copy of chromosome 21 (2n=47).} \\ \bullet & \text{Symptoms: Mental retardation, short stature, broad forehead, flattened nose, short neck, slanting eyes, and heart defects.} \\ \bullet & \text{Frequency: Common in children born to mothers above 35 years.} \\ \end{array}\] 2. Turner's Syndrome (Monosomy X): \[\begin{array}{rl} \bullet & \text{Occurs due to absence of one X chromosome in females (45, XO).} \\ \bullet & \text{Symptoms: Short stature, webbed neck, underdeveloped ovaries, sterility, and lack of secondary sexual characters.} \\ \bullet & \text{Affects only females.} \\ \end{array}\] 3. Klinefelter's Syndrome: \[\begin{array}{rl} \bullet & \text{Occurs in males having an extra X chromosome (47, XXY).} \\ \bullet & \text{Symptoms: Tall stature, underdeveloped testes, sterility, enlarged breasts (gynecomastia), and reduced facial hair.} \\ \bullet & \text{Affects only males.} \\ \end{array}\] Conclusion:
These syndromes arise due to non-disjunction of chromosomes during gamete formation. They significantly affect physical and mental development.