I remember from my Biology classes the inactivation of the X chromosomes in females. All cells in a female body have the sexual chromosomal pair as XX. However, they are clever and during development, these inactivate one of those to prevent overflow of information. So in the end there is only one X chromosome active & the other inactive. The catch is, it happens at random unless there is faulty genetic code in one (leading to that being deactivated).
This just makes every woman even more different in they own unique way.
In the end we are sacks of particles with unpredictable (probabilistic) patterns.