Boy And Girl Identical twins
It is very rare, but it is possible for identical twins to have different sexes. They typically start as identical male twins, which means that they possess XY chromosomes and not XX. After the egg breaks off in two, one twin might lose the Y sex chromosome and turn to X due to a genetic mutation. This is known as Turner syndrome. There is only a single X chromosome, so the twin might look female but suffers from early developmental difficulties and eventual fertility problems. This does not affect the other twin.
Boy And Girl Identical Twins
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