Which condition describes females born with only 1 X chromosome?

• A. Klinefelter syndrome
• B. Turner syndrome
• C. Down syndrome
• D. Triple X syndrome

Answer: (B)

Turner syndrome is caused by monosomy X, meaning a female has only one sex chromosome instead of two. In this condition the karyotype is 45,X, which leads to features such as short stature, a webbed neck, underdeveloped ovaries and infertility, and possible heart defects. Diagnosis is confirmed by analyzing the chromosomes in a blood sample. Other conditions involve different chromosomal patterns (for example, an extra X in females or an extra chromosome in males, or an extra chromosome 21), so they do not describe females born with only one X chromosome.