This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mendelian Disorders: Single-Gene Defects, Subject name: Pathology
Barr body is absent in - 
Select and explain. 
A. Kleinfelter, B. Turner, C. Super female, D. None of the above
B: Turner
Answer: B: Turner 
Explanation: Ans. is 'b' i. e., Turner Barr body (Sex- chromatin)o It is a densely staining inactivated condensed 'X' chromosome that is present in each somatic cells of female,o It is found in the nucleus.o It is used as a test of genetic femaleness - it is possible to determine the genetic sex of an individual according as to whether there is a chromatin mass present on the inner surface of the nuclear membrane of cells with resting or internment nuclei. Remember following fact and the question will seem very easy.o Chromatid body (Barr body or sex chromatin) is derived from one of the two X-chromosomes which becomes inactivated.o The numer of Barr bodies is thus one less than the number of X-chromosomes.Now see each option one by oneo Kleinefelter's syndrome (XXY) - Two 'X' chromosomes - 1 Barr body (2-1).o Turner syndrome (XO) - one 'X' chromosome -No Barr body (1-1 =0).o Superfemale (XXX) - Three 'X' chromosome -2 Barr bodies (2-1).Note-o Barr body is found in female but :-Kleinefelter syndrome is male with Barr body.Turner syndrome is female without Barr body.