This source states that there are Barr bodies in 0-4% of males.

Why isn't it complete 0%? why some males loose their only X chromosome? How does then their body compensates for those genes which are inactivated?


To understand how the X inactivation can occur in, it requires a bit of understanding of how Barr bodies come about.

The main key players to keep in mind are (From 1):

  1. Xist: Xist Required for initiation of X-inactivation
  2. Tsix: Tsix (It's Xist spelled backwards!) Represses Xist expression by silencing the Xist promoter, also required for X-chromosome pairing, counting the number of XICs (X-inactivated chromosomes)

From 2, Here is a general diagram of how X-inactivation occurs.

enter image description here

X-inactivation requires first, count how many X chromosomes are present (n). Then, the (n-1) number of X chromosomes are inactivated. The choice for which gets inactivated is largely random.

Therefore, if a male has multiple X-chromosomes (as in the case of Klinefelter syndrome) then X-inactivation would occur in males. However, there is also the case that erroneous counting may lead to the inactivation of the only X chromosome in males early in a developing embryo. But this is lethal, and the embryo would die.

More about Kleinfelter Syndrome can be found here: Klinefelter syndrome

  1. Guided by RNAs: X-inactivation as a model for lncRNA function.
  2. Lessons from X-chromosome ina ctivation: long ncRNA as guides and tethers to the epigenome
  • $\begingroup$ So all males with Barr bodies are Klinefelter males? $\endgroup$
    – Willk
    Nov 11 '17 at 2:27
  • $\begingroup$ If they only have 1 X-chromsome and is inactivated, they would not make it to full term. They can have more than XXY, however, there will always be multiple X's. $\endgroup$ Nov 11 '17 at 6:47

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