Fig. (3).
Incomplete HERVs are derived from mutations affecting the various genetic domains and LTRs. There are two conflicting theories for the origins of the LINEs and SINEs. One theory posits an independent evolution within the genome. The other posits that they are breakdown products of endogenous retroviruses, which subsequently developed their own evolutionary trajectories. Functionally they interact with one another, so should be considered as related groups.