sentences:  Some features may not be present "in vivo" or may be absent "in vitro".In May 2007 evidence in support of the Immortal DNA Strand theory was discovered by Michael Conboy et al., using the muscle stem/satellite cell model during tissue regeneration, where there is tremendous cell division during a relatively brief period of time.Using two BrdU analogs to label template and newly synthesized DNA strands, they saw that about half of the dividing cells in regenerating muscle sort the older "Immortal" DNA to one daughter cell and the younger DNA to the other.