This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
Barr body is absent in female having 
Select and explain. 
A. 46 XX genome, B. 45 X0 genome, C. 47 XXX, D. All of the above
B: 45 X0 genome
Answer: B: 45 X0 genome 
Explanation: Barr body is absent in those with genotype 45 XO . For a brr body to be present a minimum of 2 x chromosomes should be there . No of Barr body = no of x chromosomes - 1. Reference: GHAI Essential pediatrics, 8th edition