This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
XXY klinfilter which has extra? 
Select and explain. 
A. X-chromosome, B. Y chromosome, C. Both, D. None
A: X-chromosome
Answer: A: X-chromosome 
Explanation: Ans. is 'a' i.e., X-chromosome The major numerical disorders of chromosomes are 3 autosomal trisomies Trisomy 21 -- Down syndrome Trisomy 18 -- Edwards syndrome Trisomy 13 -- Patau syndrome Four types of sex chromosomal aneuploidies: Turner syndrome (usually 45,X) Klinefelter syndrome (47,XXY) 47,XXX 47,XYY By far the most common type of trisomy in liveborn infants is trisomy 21 (karyotype 47,,+21 or 47,XY +21) or Down syndrome.