This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Molecular Genetics, Subject name: Biochemistry
A 20-year-old female presents for an infertility workup. She has never had a menstrual period. She is short with a broad chest, webbed neck, and low-set ears. It is demonstrated that she has an abnormal karyotype.Which one of the following best describes the cause of this genetic abnormality? 
Select and explain. 
A. Trisomy, B. Monosomy, C. Trinucleotide repeat, D. Translocation
B: Monosomy
Answer: B: Monosomy 
Explanation: This patient has Turner syndrome or 45 XO. She is missing a second sex (X) chromosome. She would not have a Barr body and would be infertile. She is phenotypically female.