Answer: Chromosomal disorders are abnormalities caused by a change in the number (aneuploidy) or structure of chromosomes, usually due to non-disjunction of chromosomes during gamete formation.
Turner’s syndrome (44 + XO, 45 chromosomes):
- Caused by the absence of one X chromosome (monosomy of X), due to fusion of a normal egg with a sperm lacking a sex chromosome (or vice versa).
- Individuals are females with short stature, webbed neck, broad shield-like chest and widely spaced nipples.
- Ovaries are rudimentary, they are sterile and secondary sexual characters are poorly developed (no menstruation).
- Some may show reduced intelligence.
Klinefelter’s syndrome (44 + XXY, 47 chromosomes):
- Caused by the presence of an extra X chromosome in a male, due to non-disjunction of X chromosomes.
- Individuals are males, tall with long limbs, with small testes; they are sterile (no sperm production).
- They show some female characters such as development of breasts (gynaecomastia), sparse body hair and feminine fat distribution.
- They may show mental retardation.
