Is X inactivation really important? Why don’t the dominant genes on one chromosome mask the recessive on the other chromosome? This happens in other sets of chromosomes so why exactly does this happen in the sex chromosomes of a female?

And during x inactivation in the blastula isn’t there a heightened possibility of getting a disorder since you might be inactivating the normal genes and allowing the x linked recessive disorder to show up?

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    $\begingroup$ Welcome to SE Biology. Please read the Tour and consult the Help on asking questions. You will see that you are expected to do some research before posting. Where have you looked for articles about X-inactivation? I imagine any account would explain why it is necessary and perhaps even mention alternative positive compensation mechanisms in other species, eg Drosophila. If this is still unsatisfactory come back and tell us why. $\endgroup$
    – David
    Commented Sep 21, 2019 at 16:00
  • $\begingroup$ Out of frustration I have to say to all downvoters, that I found this question, particularly the last sentence, helpful. I understand that we are supposed to do the research first but it is not helpful when the first thing you do is downvote us. $\endgroup$ Commented Mar 3, 2023 at 13:17

1 Answer 1


If both X's are active gene expression is doubled which causes all sorts of abnormalities. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1686009/

a good and short explanation of X inactivation - https://www.youtube.com/watch?v=Y9vXhmI5FXM

Not all cells have the same X inactivated. It happens randomly so women are mosaics of lineage cells with different Xs. If there is a disorder due to bad mutation in one X, it's not present in all cells. This is the reason why boys with MECP2 gene mutation die shortly after birth while girls can live with Rett syndrome. Because not all cells carry the mutation so it's not as bad compared to when boys inherit it

  • $\begingroup$ Hi Retardi Grade, I see your profile says you are an independent researcher. Is there any way I can get in touch with you? $\endgroup$ Commented Mar 3, 2023 at 13:50

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