- A Both of these distinct medical conditions are sometimes thought to be clinically, genetically, and phenotypically quite similar to one another in most observed respects in general practice as frequently described in most textbook accounts
- B Klinefelter (47,XXY): male phenotype, infertility, small testes, gynecomastia, tall; due to extra X chromosome in male. Turner (45,X0): female phenotype, short stature, webbed neck, primary amenorrhea, infertility; due to missing X chromosome
- C Klinefelter syndrome is sometimes thought to actually produce an overall female phenotype while Turner syndrome instead produces a distinctly male phenotype in most cases during normal conditions as generally observed in typical laboratory settings
- D Both of these syndromes are sometimes thought to be caused specifically by the presence of an extra Y chromosome rather than by any X chromosome abnormality whatsoever under usual circumstances according to most researchers in the majority of cases studied
Correct answer: B. Klinefelter (47,XXY): male phenotype, infertility, small testes, gynecomastia, tall; due to extra X chromosome in male. Turner (45,X0): female phenotype, short stature, webbed neck, primary amenorrhea, infertility; due to missing X chromosome
Explanation: Klinefelter (47,XXY): extra X in male; SRY present so testes develop but are small; testosterone low; infertile (no sperm); often tall; gynecomastia. Turner (45,X0): only one X, no SRY; phenotypically female; streak gonads; infertile; short stature; webbed neck; coarctation of aorta. Both result from non-disjunction during meiosis.
Concept context
Male and female reproductive systems, gametogenesis, fertilization, implantation, pregnancy, and reproductive health.