Mothers Keep the DNA of Their Sons

Mothers keep the DNA of their children in their system for a lifetime, particularly the genes of male offspring.  The DNA resides in the mother's brain.  It is not know what the overall effect is on a woman.  It was found, however, that presence of male DNA reduced the incidence of Alzheimer's.

All mammals exchange DNA in this way.  It is called fetal microchimerism and has bad effects as well as good.  While improving disease resistance it can lower autoimmune reactions.

Until recently humans were not known to have microchimerism, though other animals such as rats did.  Autopsies on middle aged deceased woman found male DNA spread throughout the brain.  A 101 year old lady had DNA present even at her advanced age.
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