Normally a female human has an X allosome from her father and an X allosome form her mother. What if an double mutation happened, which causes that someone has two X allosomes form her mother and no allosomes form her father? Will this person be a normal female?

Note that it is both possible that there are no allosomes form the father or mother (known as Turners syndrome, (45, X)) and that there are two X allosomes form the mother (known as (47, XXX) and (47, XXY) respectively).

Since the Turner syndrome happens for 1 in 5000 births, and the Triple X syndrome happens for 1 in 1000 births, I estimate that this would happen once in 5 million births.

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    $\begingroup$ Is your question Can a female (human) be "normal" if her two Xs are exactly the same, that is if she is homozygous at all sites on the allosomes?? $\endgroup$ – Remi.b Oct 2 '15 at 19:16
  • $\begingroup$ @Remi.b I somehow didn't realize that would imply it. Yes that is basically the question, however, I am not sure if there wouldn't be other consequences. $\endgroup$ – wythagoras Oct 2 '15 at 19:27
  • $\begingroup$ It does not necessarily imply this. If the two Xs come from the mother, then with probability 0.5, she may receive the two different chromosomes (let's assume no recombination for ease). In which case, she wouldn't be any different from her mother for the sex chromosomes. If the two Xs are the exact same then, she will likely suffer from some level of inbreeding depression but she might be fine. $\endgroup$ – Remi.b Oct 2 '15 at 19:37
  • $\begingroup$ Causality is not causation. Be careful with 'estimates' like that. $\endgroup$ – BAR Oct 2 '15 at 20:05
  • $\begingroup$ Turner syndrome occurs in about 1 in 2,500 female births. $\endgroup$ – BAR Oct 2 '15 at 20:07

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