by Jamie Henzy — The line be­tween viruses and par­a­sitic el­e­ments of the genome is thin and del­i­cate, and prob­a­bly of­ten crossed. Par­a­sitic el­e­ments that ac­quire the means to es­cape the host cell be­come viruses and, con­versely, viruses can lose this abil­ity and re­turn to a more...