AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

KLINEFELTER SYNDROME

• Named after Dr. Harry Klinefelter, an endocrinologist at Massachusetts General Hospital , who first described it in 1942.
• Extra copies of genes on the X chromosome interfere with male sexual development, preventing the testes from functioning normally and reducing the levels of testosterone.
• Klinefelter syndrome affects 1 in 500 to 1,000 males.
• Other names people use for Klinefelter syndrome
  • Klinefelter's Syndrome
  • 47,XXY
  • XXY syndrome
  • XXY trisomy
• Affected males have one extra copy of the X-chromosome in each of a male's cells (47,XXY).

Main phenotypic characteristics

• Learning disabilities and difficulty with speech and language development.
• Quiet, sensitive, and unassertive, but personality characteristics vary among males with this condition.
• A shortage of testosterone during puberty can lead to breast enlargement (gynecomastia), reduced facial and body hair, and an inability to father children (infertility).