sentences:  A pulse of DNA label is given to adult stem cells under conditions where they have not yet delineated an immortal DNA strand.During these conditions, the adult stem cells are either dividing "symmetrically" (thus with each division a new 'immortal' strand is determined and in at least one of the stem cells the immortal DNA strand will be marked with DNA label), or the adult stem cells have "not yet been determined" (thus their precursors are dividing symmetrically, and once they differentiate into adult stem cells and choose an 'immortal' strand, the 'immortal strand' will already have been marked).Experimentally, adult stem cells are undergoing symmetric divisions during growth and after wound healing, and are not yet determined at neonatal stages.